IBM Model M keyboards

IBM's sixth generation of keyboards (aka, IBM Model G, IBM Keyboard G, IBM Keyboard M, IBM Type M or IBM Model-M)

IBM Keyboard M (printed as "Model M" in production, originally "Keyboard G") is a large family of computer keyboards created by IBM and later sustained by Lexmark, Unicomp, and Toshiba Global Commerce Solutions (TGCS). It is IBM's sixth generation of keyboards, following the older but related Model F family. The sole unifying principle of the Model M family is the use of membrane sensing circuits whilst mostly being flagship products in their respective target market segments; whilst membranes are common today, IBM's adoption of it contrasted the capacitive assemblies used by IBM's previous two major families of keyboards - the aforementioned Model F family and the earlier Model B family. Other common well-known features found on Model Ms include membrane buckling spring switches and plastic riveted assemblies, although not all Model Ms featured either, making the family less unified in designs than previous generations.

Today, buckling spring Model Ms are regarded as one of the best families of keyboards created due to their unique auditory and tactile feedback characteristics. Whilst perhaps only bested by IBM's earlier creations in this regard, the Model M family is in turn more diverse and such keyboards can feature more 'digestible' modern-looking physical layouts, are typically cheaper to buy, and there is a superior availability of spare parts should they be needed. Some consider Model Ms to also be a "gateway drug" into the wider field of vintage and/or IBM keyboards.

Contents

History

The story of the Model M family begins in late 1983 when IBM patented the membrane buckling spring keyswitch design invented by Edwin T. Coleman, III. According to the patent, the main intent of this design was to half the production cost of the buckling spring switch compared to Richard Hunter Harris' 1977 capacitive buckling spring design used in Model F family keyboards^[1][1]
IBM - Rocking switch actuator for a low force membrane contact switch [accessed 2021-06-17].. The keyswitch was put into production the following year, with the first vessels of the Model M DNA being typewriter-bound keyboard assemblies. Namely those for the IBM 6746 Wheelwriter 3, 6747 Wheelwriter 5 and 6750 Quietwriter 7, which were all released by 13th December 1984^[2][2]
Hattiesburg American - Archives: The Blitz is On… IBM [accessed 2021-06-17]., although production on their keyboard assemblies started ahead of that date. Model M based keyboards made as early as June 1984 (a Wheelwriter 5 keyboard) have been recorded^[3][3]
ASK Keyboard Collection - SNKB-M1984-WWA-75 [accessed 2023-07-29]. License/note: CC-BY-NC-SA 4.0..

The first discrete (designed to be used as a separate, distinct device) keyboard with membrane buckling springs was the IBM Enhanced Keyboard, which was announced across May and June 1985 in the forms of the IBM 7531/7532 Industrial Computer Keyboard^[4][4]
IBM - IBM 7531 Industrial Computer Brief Description of Announcement, Charges, and Availability [accessed 2022-01-20]. and IBM 3161/3163 ASCII Display Station Keyboard^[5][5]
theMK#1822 - donated photos. License/note: CC BY-NC-SA 4.0 (cropped). respectively. The Enhanced Keyboard was developed as a "low-cost, high-volume" but still "excellent quality" keyboard by a team assembled at IBM U.S. Lexington consisting of personnel from IBM's Information Products Division, Communication Products Division and Entry Systems Division. Special emphasis was placed on developing what would become the Enhanced layout, which was tested by research human factors groups in Lexington, White Plains, Kingston, Boca Raton and San Jose. At this stage, the keyboard was designated "Keyboard G"^[6][6]
IBM - Lexington Today - New IBM Product Features Lexington Keyboard [accessed 2024-05-19]. License/note: accessed via a deskthority post courtesy of rocco_16v & photo excerpts used under fair dealing..

By the time of production in the United States, the keyboards finally bore the "Model M" designation. In the United Kingdom, early production sometimes bore a "Model G" designation on a sticker inside instead. The following April, home and office PC versions of the Enhanced Keyboard such as P/Ns 1390120 (PC/XT) and 1390131 (PC/AT) and their regional counterparts were released^[8][8]
IBM - IBM Enhanced Keyboard for the Personal Computer Brief Description of Announcement, Charges, and Availability (#ZG86-4008) [accessed 2023-07-29].. 1987's P/N 1391401 (PS/2) and its regional counterparts are the most recognisable and cemented the reputation of the Model M and the status of the Enhanced Keyboard being the definitive member of the family.

Meanwhile, the Model M family was also expanding with several types of 122-key terminal keyboards (Converged Keyboard), 84/85-key tenkeyless keyboards (Space Saving Keyboard or "SSK"), and various smaller keypads. IBM also released follow-ups to the original Wheelwriters and Quietwriters that all used Model M-based keyboard assemblies, including 1985's 6770 Wheelwriter System and 6780 Quietwriter System^[9][9]
IBM - IBM Selectric System/2000 Systems - Wheelwriter/Quietwriter Brief Description of Announcement, Charges, and Availability (#185-109) [accessed 2023-02-26]., 1986's 6747-2 Wheelwriter 6 and Quietwriter 8, and 1988's Wheelwriter Series II line-up and 6779 Personal Wheelwriter Typewriter^[10][10]
IBM - IBM typewriter milestones (page 2) [accessed 2023-07-29]..

The 1990s were very eventful for the Model M family, with the early '90s seeing the formation and sale of IBM Information Products Corporation in August 1990 and March 1991 respectively to facilitate the divestiture of IBM’s Lexington, KT and Boulder, CO typewriter and keyboard manufacturing operations^[11][11]
Los Angeles Times - IBM Planning to Set Up New Subsidiary : Industry: A buyout firm will be the majority owner of its typewriter and keyboard operations [accessed 2021-09-01].. This resulted in the formation of Lexmark International, which IBM subsequently started marketing some of their products with IBM branding (including Model M keyboards and typewriters using them)^[12][12]
IBM - Archives: 1990s - 1991 [accessed 2024-08-11]. License/note: retrieved via Wayback Machine (2023-08-02 capture). with a five-year contract to do so in the case of printers^[13][13]
Peter H. Lewis @ The New York Times - The Executive Computer; Can I.B.M. Learn From a Unit It Freed? [accessed 2023-07-29].. Lexmark became the primary manufacturer of PC-compatible Model Ms destined for North America, though IBM factories elsewhere in the US (and in the UK and Mexico) continued their own production for different markets and/or segments other than PC-compatible. The '90s also saw the rise of numbered Model M variants, resulting in M1 through M15 (excluding M10, M12 and M14) being used as designations for unique keyboard designs sequentially from 1990 to 1994. The family also gained numerous members that did not use buckling springs, instead using technologies such as Quiet Touch-branded rubber domes (IBM Basic Keyboard) or buckling rubber sleeves (M3, M4/M4-1, M6/M6-1, M7/M7-1, M8, M9 and M11). Attempts to combine keyboard and pointing devices were also made, with keyboards featuring integrated trackballs (M5-1/M5-2) and TrackPoint pointing sticks (M4-1, M6/M6-1, M13) being released between 1992 and 1994. IBM also marketed "Wheelwriter by Lexmark" branded Wheelwriter models during this time.

By 4th December 1995, Lexmark had made the decision to exit the keyboard market by April 1996 to focus on printers. For 1994, keyboard sales accounted for 11% of the company's revenue and just 5% of its gross profit. The five-year agreement between IBM and Lexmark previously had was due for renewal, but its terms were being reworked^[15][15]
Clare Goldsberry @ Plastic News - LEXMARK EXITS KEYBOARDS, TARGETS PRINTERS: FIRM TO OUTSOURCE MORE MOLDING [accessed 2023-07-29]. License/note: retrieved via Wayback Machine (2022-08-10 capture). and no longer included keyboards when it was signed on 25th January 1996^[16][16]
Lexmark - Lexmark International Announces Supplies Trademark Agreement With IBM [accessed 2023-07-29]. License/note: retrieved via Wayback Machine (1998-02-09 capture).. Assets related to buckling spring, buckling sleeve and Quiet Touch rubber dome Model M keyboard production such as tooling (including 32 presses and all related auxiliary equipment) were sold off. As part of the new agreement, IBM purchased "certain" keyboard assets back from Lexmark. Maxi Switch bought Lexmark's manufacturing rights, patents (including the 1983 membrane buckling spring patent), and assets for the Lexmark Select-Ease Keyboard (Model M15) and rubber dome keyboards. Due to this, Maxi Switch OEM buckling sleeve Model M7^[17][17]
ASK Keyboard Archive - P/N 92F6320 (2000, Maxi-Switch) [accessed 2023-07-29]. License/note: archived from volatile eBay listing and used under fair dealing., M7-1^[18][18]
ASK Keyboard Archive - P/N 92F6310 (1999, Maxi-Switch) [accessed 2023-07-29]. License/note: archived from volatile eBay listing and used under fair dealing., M8^[19][19]
ASK Keyboard Archive - P/N 92F6330 (1998, Maxi-Switch) [accessed 2023-07-29]. License/note: archived from Recycled Goods and used under fair dealing., M9^[20][20]
ASK Keyboard Archive - P/N 92F6271 (1998, Maxi-Switch) [accessed 2023-07-29]. License/note: archived from volatile eBay listing and used under fair dealing. and M11 and buckling spring M13^[21][21]
ASK Keyboard Archive - P/N 92G7461 (1996, Maxi-Switch) [accessed 2023-07-29]. License/note: archived from volatile eBay listing and used under fair dealing. keyboards began appearing from 1996 onwards. Manufacturing of other buckling sleeve Model Ms such as the M4 and M6 family fell to Key Tronic^[22][22]
ASK Keyboard Archive - P/N 84H8525 (1996, Key-Tronic) [accessed 2023-07-29]. License/note: photos donated by jugostran.^[23][23]
ASK Keyboard Archive - P/N 42H3979 (1996, Key-Tronic) [accessed 2023-07-29]. License/note: photos donated by volvob5234t..

Also in 1996, a group of former Lexmark (and in some cases former Lexmark and IBM) employees retired from the company to form Unicomp to continue to produce buckling springs and Quiet Touch Model Ms based on the last generation designed by IBM and Lexmark. Since tooling had already been sold off back to IBM and Maxi Switch by the time of Unicomp's founding, the fledging company spent the rest of the '90s recovering Model M tooling from other Model M factories under IBM and Maxi Switch to rebuild its tool base^[24][24]
u/funkmon - I typed on the new Unicomp SSK. *Write-up of visit to Unicomp* [accessed 2022-02-20].. By the turn of the millennium, Unicomp had established a wide range of keyboards and began the current era of the Model M. Unicomp continued to produce buckling spring Model Ms for IBM as late as 2004^[25][25]
ASK Keyboard Collection - SNKB-M2004-13U-101 [accessed 2021-06-17]., and 2012 was the last year IBM marketed any Model Ms in their name as they then sold its IBM Retail Store Solutions division to Toshiba TEC^[26][26]
IBM - Toshiba TEC to Acquire IBM’s Retail Store Point-of-Sale Solutions Business; Agreement Allows Both to Tap Growing Smarter Commerce Opportunity [accessed 2021-06-17].. Toshiba TEC formed TGCS, who then continued production of the Models M7 through M11 keyboards under their own name.

Design

Possible keyswitches & membrane assembly

The Model M keyboard family makes use of several overall keyswitch designs, but at the core of all of them is a membrane assembly used for simple ohmic sensing. A membrane assembly is a form of layered circuitry where traces for a keyboard matrix are spread across two thin plastic sheets separated by a third non-circuit spacer sheet. Each circuit sheet will have many halves of a pair of contact points that register a key when pushed together through the spacer sheet by some actuator. Membrane assemblies are used as a cheaper alternative to hard PCBs^[28][28]
deskthority wiki - Membrane keyboard [accessed 2021-09-09].

Despite a membrane assembly simply being a type of circuit, they are often confused and conflated with rubber dome actuators because the two technologies are frequently paired together for cheap keyboard designs and have gained a potentially negative connotation from that. However, a membrane assembly is practically imperceivable in most keyboard designs and provides no meaningful auditory or tactile feedback on its own. The real trade-off for using ohmic membrane assemblies compared to hard PCBs is that their thin, flexible nature makes it difficult to embed diodes to prevent ghosting, thus keyboards that use these must employ blocking and are limited to two-key rollover. For Model Ms, three complete keyswitch designs are known:

Buckling springs

More information: IBM buckling spring#IBM membrane-type

Buckling springs are an actuator design where the said spring when pressed deforms (buckles) in a specific way that allows a pivot plate (also called a flipper, rocker or hammer) to hit the circuit underneath to make a connection. At rest, the pivot plate is held upwards from any circuit underneath. In the case of Model M keyboards with them, buckling such a spring will provide auditory and tactile feedback when the buckled spring strikes its surroundings and will ultimately cause the pivot plate to apply pressure and bridge two contacts on the membrane assembly below it at a given keyswitch position^[1][1]
IBM - Rocking switch actuator for a low force membrane contact switch [accessed 2021-06-17]..

This contrasts the buckling springs found on the earlier Model F keyboards that when buckling the capacitive material their pivot plates are made of is sensed by a capacitance-sensing PCB underneath^[30][30]
Deskthority Wiki - IBM Beam Spring Keyboards#4978 [accessed 2022-10-26].. To differentiate the two implementations, Model M's style of buckling springs is generally referred to as membrane buckling springs. Because the pivot plates accomplish their purpose before their buckling springs are fully compressed, the design is said to "part-way actuate".

Buckling springs are a clicky-tactile switch considered by some to be the quintessential good clicky switch. The properties of both features are rather unique as there are seldom switches that feature a similar mechanism. It is best described as having a crisp, pingy click that perfectly matches the point of keyswitch actuation, and having tactility suited for typing but also not over the top. Buckling springs on Model Ms are rated for 25 million key presses and are also on the heavier feeling side of switches. Buckling-spring Model Ms are still produced today by Unicomp.

Buckling sleeves

More information: IBM buckling rubber sleeve

Contrary to what might be common belief, not all Model M keyboards used buckling spring keyswitches. Two other types of actuators were employed on various Model M variants by the early 1990s, and the most prolific of the two was the IBM buckling rubber sleeve (or simply "IBM buckling sleeve"). This is the provisional name of a (mostly) low-profile orientated keyswitch design developed by IBM Information Products Corporation between 1990 and 1991^[31][31]
Computerworld - 1 April 1991 [accessed 2021-12-30]. and was first used on March 1991's ^[32][32]
IBM - THE IBM PS/2 MODEL L40 SX SYSTEM AND FEATURES (#191-030) [accessed 2022-01-18]. IBM Personal System/2 L40SX laptop's keyboard assembly and numeric keypad attachment (Model M3 family). M3 subsequently served as the basis of the Models M4 and M4-1 Space Saver Keyboards and was developed into the Models M6 and M6-1 ThinkPad Keyboards. Another lineage was created for the point-of-sale sector with Models M7, M7-1, M8, M9, M11, and the "M-e" family of M7 to M11 derivatives and successors. Despite not being as well known as buckling springs, their association with many early ThinkPads and enduring IBM/Toshiba POS systems means a high number of such Model Ms was also produced.

On its own and contrasting rubber domes, "buckling rubber sleeve" refers to a type of rubber tactile element part of a keyswitch design that sits on top of a keyboard assembly instead of inside and thus doesn't play a direct role in actuating something. IBM's buckling sleeve as a keyswitch refers to such an element with a specific sculpt and a range of sizes and two main types of actuation. The membrane assembly may be actuated by a rod on a keycap acting as a plunger or a slider fixed in a keyboard frame barrel. In theory, this allows for a more solid 'bottoming-out' feel compared to a typical rubber dome over membrane keyswitch design. Buckling-sleeve Model Ms are still produced today by Toshiba Global Commerce Solutions.

Rubber domes

Despite the existence of IBM buckling sleeves, some Model Ms have a more traditional rubber dome over membrane keyswitch design. IBM, Lexmark and Unicomp marketed these as "Quiet Touch" keyboards, first introduced in 1993 with an IBM Enhanced Keyboard variant called the IBM Basic Keyboard (eg, P/N 71G4644)^[33][33]
IBM - IBM VALUEPOINT FOR AS/400 Brief Description of Announcement, Charges, and Availability [accessed 2022-01-18]. and also used for some Model M2 and 122-key Model M Converged Keyboard variants. Today, Unicomp still offers a Quiet Touch option for most of its keyboards.

Essentially, Quiet Touch rubber domes were used to replace buckling springs in existing keyboard designs, whereas buckling sleeves were used for entirely new keyboard lineages. As such, their host keyboards are exactly like their buckling spring counterparts' but the buckling spring and pivot plate assemblies are of course replaced by rubber domes across a mat. The keycaps are however specially designed to press on a dome, meaning they cannot be reused with buckling-spring keyboards. Technically, it's possible to convert a Quiet Touch Model M to using buckling springs by replacing the rubber dome mat with buckling springs and replacing all the keycaps with buckling-spring-compatible ones.

Keyboard assembly

The majority of Model M keyboards are not monocoques - the cover set (outer casing) and keyboard assembly can be easily separated. The typical Model M keyboard assembly is a sandwich of the following distinct layers:

There are some notable exceptions to the above. From the 1990s onwards, Model Ms with keyboard assemblies that more tightly integrate with the keyboard's cover set were introduced. The known cases include:

Fastenings for buckling spring Model M assemblies

Model M keyboard assemblies are typically riveted together from their keyboard frames to base plates in some way to provide security for the inner keyswitch technology with tension. Typical buckling spring Model Ms famously use melted plastic rivets, which are melted from plastic stalks that protrude from the keyboard frame into many holes in the base plate. The longevity of these rivets has been called into question as they can invariably break off over the years and decades. Losing a handful of rivets that are not adjacent to each other is generally not fatal, but losing many that are clustered in one area of the keyboard will lead to a loss of tension that can at first lead to mushy-feeling keypresses and then will stop registering as it gets worse. It's impossible to establish the cause from case to case, but some generally believe they can break with a combination of extreme and/or sustained vibration, humidity and the user's handling of the keyboard.

The positive news is that a chronic loss of rivets typically does not mean the keyboard cannot be salvaged. Practises known as screw or bolt modding can be used to replace the lost rivets with screws or bolts (respectively) to regain tension on the assembly. This can be done yourself (guides on how to do this like Bitten's Model M Restoration Megaguide exist) or can be professionally done by experienced 'bolt modders' such as long-time practitioner Brandon @ clickykeyboards.com. It should also be considered that many vintage Model Ms from the 1980s continue to operate with their original rivets intact, and indeed many Model Ms exchange hands between owners without issue.

The IBM PS/2 50-key Function Keyboard, Screen Reader Keypad and Model M1/M2 Selectric Touch keyboards are the only major buckling spring capable Model Ms that don't use plastic rivets.

Fastenings for buckling sleeve Model M assemblies

As for non-buckling spring Model Ms such as those with IBM buckling sleeve keyswitches, the method of keyboard frame to base plate security varies. Model M4, M4-1, M6 and M6-1 family alphanumeric keyboards use metal hooks that orginate from the base plate and slide into position into the keyboard frame. This solution avoids perishable plastic and allows the base plate to be easily removed from the rest of the keyboard.

Model M3, M4 and M4-1 numeric keypad assemblies are essentially the same and used plastic rivets.

IBM RPOS Models M7, M7-1, M8, M9 and M11 keyboard assemblies' method of security switched during their production. Generally speaking, early RPOS keyboards made by Lexmark and Maxi Switch used melted plastic rivets and later examples made by XAC, XSZ and TCGS used screws instead. Pre-MPOS and MPOS Model M-e alphanumeric keyboards all use screws.

PBT dye-sublimated keycaps

Pearl white Model Ms are known for their high-quality unique-mount PBT dye-sublimated keycaps, something inherited from the Model F family. Versus the most common keycap material, ABS^[37][37]
WASD Keyboards - Mechanical Keyboard Guide [accessed 2022-07-01]., PBT is more durable, does not degrade/yellow with age, UV or heat exposure, and will keep its texture for longer without shining^[38][38]
Switch And Click - ABS vs PBT Keycaps: What’s the Difference? [accessed 2021-09-09].. Dye-sublimation is also a very durable text printing method that sinks dye material into the keycap's plastic itself, meaning there is nothing to quickly wear off as would be the case with pad-printing or silk screening. This means many vintage Model M keycaps will still be in good condition, requiring at most a good cleaning.

Most buckling spring, buckling sleeve and Quiet Touch Model M keycaps are uni-profile, meaning a given keycap can be swapped with another provided they are of the same unit size. This allows every Model M to have innate layout customisability without the user needing to worry about mismatches in keycap sculpting - sculpture is instead provided by the curved internal keyboard assembly (or the keyboard is intended to be low and uni profile, such as with Models M1, M2, M3, M4 and M6). All Model F keycaps and keycaps from curved assembly buckling spring Model Ms are fully interchangeable granted the correct unit size. Furthermore, most buckling spring Model Ms have two-piece keycaps that allow the user to swap around their layout around without needing to completely dismount the entire keycap. The two pieces are known as the stem (the part that always stays in the barrel) and the keytop (the part that can be easily swapped). That said, not all buckling spring Model Ms have two-piece keycaps, with notable exceptions including the Models M1, M2, M13 and M15, and some models that are known to have two-piece keycaps may come with single-piece keycaps due to manufacturing nuances over the years. Since 2020, Unicomp seems to now only focus on manufacturing single-piece keycaps.

Pearl white and industrial-grey coloured Model Ms receive two colours of keycaps; off-white (also known as pearl) and grey (pebble). Today, Unicomp offers keycaps in a variety of colours and as blanks or with dye-sublimated legends on their website. They can be bought individually or as part of the many predefined sets they offer^[39][39]
Unicomp - Buttons [accessed 2021-09-15]..

Pad-printed keycaps on black keyboards

Black Model Ms with all-black keycaps (such as most Model M6s and M6-1s, and raven black Model M4-1s and M13s) had pad-printed (perishable) lettering since dye sublimation cannot be used to sink in dye lighter than the host plastic without resorting to a more costly inverse dye sublimation technique.

Keycap stabilisers

To mitigate binding on multi-unit-sized keycaps, Model Ms employed two main methods of stabilising - wire stabilising and plastic insert stabilising - with the exact use and implementation depending on the year of manufacture, keycap profile and keyswitch design. Wire (or bar) stabilisers are usually rectangular, close to the keycap's footprint in size, and are used to distribute force over itself. The keyboard frame will have two clips per key to hold them in place. Plastic insert stabilisation requires the keycap to have a protruding rod about the length of the key's stem, which is received by the aforementioned inserts placed in disused barrels. The inserts are designed to keep the keycaps aligned and prevent one side from being able to travel further than the other.

Buckling spring/Quiet Touch rubber dome (standard profile)

Standard-profile Model M keycaps only received stabilisers if they were larger than 1.5 units. Wire stabilisers were always used for the spacebar, and originally also for 2-unit or larger horizontal and vertical keycaps. Wire stabilisers on horizontal (such as shift and typewriter Code) keys longer wider than 1.5 units were generally limited to early IBM Wheelwriter and Quietwriter keyboard assemblies from 1984 and 1985 but they were already being replaced with plastic insert stabilisers as early as Q2 1985^[42][42]
ASK Keyboard Archive - P/N 1351000 (1985, IBM-NL) [accessed 2024-02-04]. License/note: photos saved from volatile eBay listing, used under fair dealing.. Vertical keys used wire stabilisers for longer but were also phased out and replaced with plastic inserts from approximately 1987 onwards. The plastic inserts for horizontal and vertical keys were unique and generally colour-coded (though the exact two colours have changed over the years and from factory to factory), with the former having its hole centred and the latter having its hole aligned closer to the top (for ISO Enter/Return/Field Exit keys) or bottom (numeric keypad + and Enter/Field Exit keys).

Buckling spring/Quiet Touch rubber dome (M1/M2 profile)

Models M1 and M2 use wire stabilisers but they're mostly plastic instead of metal. The spacebar has a plastic wire with a noticeable V-shape in the middle and two protruding nobs adjacent that are supposed to be caught by retainer clips that face opposite to each other on the keyboard frame. The Enter/Return keys on ISO-layout keyboards are the only M1/M2 keycaps to use a metal wire stabiliser. Other keys that are 2 units or longer/taller use a simpler plastic wire compared to the spacebar's. Horizontal multi-unit keycaps also have a second fully-moulded key-stem, whereas vertical multi-unit keycaps have a second simpler key-stem.

Buckling sleeve (M3/M4/M4-1/M6/M6-1 style)

Non-point-of-sale buckling sleeve Model Ms exclusively use metal wire stabilisers for any key larger than 1 unit.

Buckling sleeve (M7/M7-1/M8/M9/M11/Pre-MPOS/MPOS style)

On point-of-sale buckling sleeve Model Ms, stabilisation differs between standard and relegendable keys. Standard keys larger than 1.25 units receive stabilisation; spacebars, ANSI-style left shift and all right shift keys use a metal wire stabiliser, but keys smaller than that instead rely on protrusions in each corner of the keycap to keep it level. 2-unit relegendable keys simply use two key-stems (with buckling sleeves present) for stabilisation, which means they feel heavier to press and require software configuration to disable or ignore one of them to prevent registering two keys.

Rear labels

More information: Keyboard Rear Labels topic

One of the hallmarks of the Model M family is strong documentation of the keyboard's type and date of manufacture in the form of a rear label sticker casually referred to as a 'birth certificate'. This feature is something also inherited from the Model F family and has been present since the first Wheelwriter keyboard assemblies were produced and are still found on the latest TGCS POS or Unicomp buckling spring Model Ms. Model M keyboards can have an external label and an internal label.

External rear labels

The external rear label is used to display information about the keyboard as a whole. As a summary of the main data points of interest presented on the external rear label:

There are many variations of these birth certificates from various eras of production or manufacture. A sample can be seen below but note there are many more as well.

Internal rear labels

As briefly mentioned above, the internal keyboard assembly (of Model Ms that are not a unibody design) can have their own part number with their own rear-facing label. Actionwriter, Quietwriter and Wheelwriter keyboard assemblies typically also have their only birth certificate on the back of the keyboard assembly. The internal rear label is used to display information regarding just this inner assembly along with the keycaps fitted to it as standard. It doesn't represent the type of controller, lock-lights or cover set of the whole keyboard. As such, multiple unique outer part numbers can share the same internal part number as evidenced by the fact the US ANSI layout IBM Enhanced Keyboards P/N 1390120 (PC/XT)^[44][44]
ClickyKeyboards - 1987 IBM model M (1390120) Made by IBM 08 JAN 87 [accessed 2021-12-19]., P/N 1390131 (PC/AT)^[45][45]
ClickyKeyboards - 1987 IBM model M (1390131) Made by IBM 30 JAN 87 [accessed 2021-12-19]. and P/N 1391401 (PS/2)^[46][46]
ClickyKeyboards - 1990 IBM model M (1391401) Made by IBM 09-17-90 [accessed 2021-12-19]. can all bear the inner assembly part number P/N 1386085 since the differences between those three models don't include the keyboard assembly itself or the keycaps.

As a summary of the main data points of interest presented on the internal rear label:

Once again, a sample of these rear labels can be seen below but keep in mind that various other styles exist. Another thing to note is that internal rear labels have been known to be substituted with information written directly on the keyboard's base plate, especially for US-produced Model Ms in the 1990s.

Generations

Due to the size and diversity of the Model M keyboard family, it's impossible to establish a universal set of observed generational changes for all keyboards. As such, please refer to the "Generations" sections of individual Model M variants (if available).

Naming

Designation

More information: Major IBM Typewriter & Keyboard Models

"Model M" (the common printed marketing name) is the most commonly used term to refer to this family of keyboards and it's widely assumed that "M" refers to their mutual membrane-driven nature. Despite that, keyboards of this family could also be referred to as the following by IBM:

Before the "M" era, IBM's keyboard model letter convention used since the early 1970s increased logically, and this was the case up to and including "F". When IBM was announcing the Enhanced Keyboard design in internal communications circa June 1985, they referred to it as "G"^[6][6]
IBM - Lexington Today - New IBM Product Features Lexington Keyboard [accessed 2024-05-19]. License/note: accessed via a deskthority post courtesy of rocco_16v & photo excerpts used under fair dealing. as a continuation of this convention. But for keyboards made in the United States, "M" became the designation from production's start. In fact, should a Model M keyboard made by IBM, Lexmark, Maxi Switch or Unicomp in the US or Mexico have a "Model" designation at all, it should be based around "Model M".

IBM and Lexmark in the United Kingdom never printed "M" anywhere on their Model M keyboards though. However, early UK-made Enhanced Keyboards could have a secondary internal rear label that is either monochrome with "Model G" printed on it or blue with a large "G" printed on it.

IBM also introduced "1A" as a designation for its 122-key Model M Converged Keyboards. Early "M122s" produced in the United Kingdom could also have a secondary internal rear label that is either monochrome with "Model 1A" printed on it or red with a large "1A" printed on it. "M122s" produced in The Netherlands with particularly large cover set rear labels have "K1A" printed as their "MODEL". IBM announcement letters and some manuals treat "G", "1A" and (the not-Model-M related) "1B" as counterparts of a different, repurposed nomenclature transcending traditional IBM keyboard family designations and aimed primarily towards IBM Display Stations (terminals).

Official

Since Model Ms existed in an era where IBM products were increasingly marketed for markets beyond enterprise, the practice of formally but simply naming the keyboard after its given host system(s) was eclipsed by the practice of giving the keyboard design its own marketing name that's either descriptive or even containing buzzwords. For most Model Bs and many Model Fs, the keyboard was usually named after the host system with maybe an extra term referring to its intended operator use like "Data Entry" or "Typewriter" in the name.

This practice remained for terminal Model Ms, but unlike Model B or F, Model M was not dominated by its terminal members of the family. The most obvious shift in naming is apparent with PS/2 era Model Ms such as the "IBM Enhanced Keyboard" and "IBM Space Saving Keyboard" - the former is a marketing buzzword referring to the innovations of the keyboard's layout, and the latter is simply just descriptive. During the 1990s when Lexmark introduced many sequentially numbered Model M variants, the naming conventions were more mixed. Most desktop keyboards remained either branded or named after a pointing device technology it possesses, like IBM Space Saver Keyboard with TrackPoint II (Model M4-1), IBM Trackball Keyboard (M5) and IBM TrackPoint II Keyboard (M13). Laptop-based Model M assemblies such as M3, M6 and M6-1 were named after their host system. Models M7 through M11 were actually part of a related series dubbed the IBM Retail POS family, thus all but one of its members are named accordingly like IBM Retail POS Keyboard with Card Reader (M7) and IBM Retail ANPOS Keyboard (M9).

Lexmark blended descriptive and marketing speak for its own-branded Model Ms. Lexmark referred to its buckling spring Model Ms as "Classic Touch Keyboard" and its rubber dome ones as "Quiet Touch Keyboard". Lexmark also referred to its M2s as "Streamlined Keyboard". Unicomp carried over this practice to a degree, but occasionally also choose more abstract naming such as "EnduraPro" for its compact pointing stick keyboards. However, with the recent introduction of the "Mini Model M", Unicomp has returned to descriptive naming for its latest release.

Community

Colloquially, people today may refer to Model Ms by the number of keys a model has, via an acronym or initialism, or by its numbered designation. For example, instead of referring to "Enhanced Keyboard" by that name, they're generally referred to as "M101" or "M102" to concisely indicate the keyboard is a Model M and it has 101 or 102 keys, which more often than not will be an Enhanced Keyboard. 122-key Model Ms are almost always shortened to "M122" instead of including the name of their terminal or whether they are a "Host Connected Keyboard". As of late, the inclusion of the ASK 122-key Model M Converged Keyboard type system has also started appearing as an additional but concise way to indicate what era or featureset of M122 is in question. An example of an initialism would be "SSK" for "Space Saving Keyboard". Much like period marketing, referring to a Model M by its host system name is generally minimalised compared to Model B and Model F keyboards.

Keyboards

Model M-based typewriter keyboard (1984)

eg, P/Ns 1351000, 1351002, 1351016, 1379740, 1393780, 1396000, 1398350, 1399135

The first membrane buckling springs keyboards were in fact the keyboard assemblies for the 1984-debuting IBM Wheelwriters 3 and 5 (impact printer) and Quietwriter 7 (non-impact printer) (collectively known as the IBM Selectric System/2000). What would become the Model M as we know them featured on all subsequent IBM and later Lexmark Wheelwriters for the next decade. The layouts of these keyboard assemblies were vaguely PC-like, with a mix of including T-nav arrow keys, one or two columns of left-side function keys, and occasionally even a numeric keypad being found on various models depending on their value segment. As a result, most Wheelwriter keyboards range from approximately 65% to 80% size layouts. The common feature amongst all of them was a split spacebar with the smaller "Code" key being an additional modifier for accessing functions throughout the keyboard. Wheelwriter keyboards were produced for the entire IBM and Lexmark eras of Model M history, with examples produced as late as 2001 possibly by Unicomp^[52][52]
ASK Keyboard Collection - SNKB-M2001-WWA-92 [accessed 2022-03-06]..

Industrial Enhanced Keyboard (1985)

More information: Model M Enhanced Keyboard

eg, P/Ns 1388032, 1388044, 1390653, 1394946, 1394950

The IBM Industrial Keyboard was the first of IBM's Enhanced Keyboards - the definitive Model Ms - to be released. The Industrial Model M was launched in May 1985 for the IBM 7531 and 7532 Industrial Computers and was the first Model M that was an actual discrete keyboard. It had the honour of introducing the now ubiquitous 101+ key ANSI and 102+ key ISO layouts most keyboards since have either followed or adapted. IBM Industrial Keyboards are of course noted for their distinct grey cover set with a slight olive tint, which was designed to obscure potential dirt and damage inflicted by an industrial environment. They were otherwise electrically and mechanically the same as the equivalent PC Enhanced Keyboard of the time. All Industrial Keyboards are AT compatible, however, early examples may also have the ability to change scancodes depending on a compliant host system's requirements.

Terminal Enhanced Keyboard (1985)

More information: Model M Enhanced Keyboard

eg, P/Ns 1386303, 1386304, 1390680, 1392595, 1394204

The first Model M available in significant numbers was the terminal version of the Enhanced Keyboard. They were first introduced a month after the Industrial Keyboard for the IBM 3161 ASCII Display Station. All terminal Enhanced Keyboards lack LED lock-lights and feature an extra key compared to their industrial and PC counterparts via the splitting of the upper vertical 2u key on the rightmost column used for numeric keypad "+" into two 1u keys, resulting in a 102-key ANSI or 103-key ISO layout. The original terminal Enhanced Keyboards had silver-square badges and 240-degree pin arranged DIN plugs, but from 1987, they were rapidly supplanted by oval-style badged keyboards with 8-pin modular (ie, same style of jack as RJ-45 and ethernet) connectors. Starting in the 1990s, the OEM activities of Lexmark and Unicomp resulted in some third-party branded terminal Enhanced Keyboards being produced for the likes of Affirmative Computer Products, ComputerLabs and NLynx. Today, Unicomp-branded terminal Enhanced Keyboards can still be ordered via their custom keyboard tool.

Type I 122-key Converged Keyboard (1985)

eg, P/Ns 1386875, 1386887, 1387001, 1389098, 1389100, 1389102, 1389110, 1389112, 1389116, 1389118, 1389120, 1389124, 1389126, 1389152, 1389160, 1389162, 1389172, 1389198, 1389260, 1389262, 1390832, 1391009, 1391011, 1391014, 1391016, 1391018, 1391019, 1393656

The Type 1 122-key Model M was a continuation of the IBM Converged Keyboard family that originated as the IBM Model F keyboards, with the 122-key Model F Converged Keyboard being the most immediate predecessor. The Type 1 "M122" first appeared as the "membrane type (new type)" keyboard unit for the IBM 3205 Color Display Console by September 1985, a 7-colour console terminal intended for IBM 43X1 family IBM System/370 compatible processors that originally used "capacitance type (old type)" (Model F-based) keyboards^[56][56]
IBM - IBM 3205 Color Display Console Maintenance Information (#SY18-2121-1) [accessed 2023-10-10]. License/note: document archived by bitsavers.. Type 1 was quickly adopted for other terminals soon after, starting with the IBM 3290 Model 230 Information Panel in October 1985, which was a plasma screen IBM 3270-compatible terminal. Model 230 was released with such a keyboard as a combined alternative to the earlier 3290 Model 1 that shipped with a Type 1 104-key Model F Converged Keyboard and an optional 24/25-key Model F Keypad. Other possible Type 1 host terminals included the IBM 3179 Models 1 (3270-family) and 2 (5250-family) Color Display Stations from November 1985 onwards^[57][57]
nightismy @ eBay - IBM Model M 122 key vintage terminal keyboard 1389152 M122 [accessed 2023-10-10]. License/note: archived from volatile eBay listing, retrieved via Wayback Machine (2022-08-16 capture).^[58][58]
IBM - IBM 3179 Model 2 Color Display Station Brief Description of Announcement, Charges, and Availability (#185-148) [accessed 2023-10-10]., the IBM 3193 Model 1 Display Station (3270-family) released in June 1986^[59][59]
IBM - IBM 3193 Display Station Brief Description of Announcement, Charges, and Availability (#186-118) [accessed 2023-10-10]., and eventually the IBM 3180 Models 1 (3270-family) and 2 (5250-family) Display Stations and IBM 3270 Personal Computer AT (aka, IBM 5273). Specialised Type 1 "M122s" were also released, including one for IBM PC3270 terminal emulation (specifically P/N 1393656).

Like its Model F predecessor, early "M122s" such as Type 1 are often nicknamed today as "battleship" or "battleship-sized" keyboards due to their sheer size. Besides the Model M-based FIB Keyboard Controller, "M122s" are in general the largest Model M keyboard designs. Being a Converged Keyboard, they have their recognisable top 24-key and lefthand side 10-key function key banks. The 24 keys typically have either "PFxx" (IBM 3270-style) or "Cmdxx" (IBM 5250-style) nomenclature legends. "M122s" typically used typewriter-style functional layouts, but data entry versions were technically available with IBM Card Punch-style alphanumeric legends. For the IBM 527X and PC3270 keyboards, they additionally had blue sublegends to differentiate PC-only functionality to terminal-only/universal functionality much like the later Type 4 122-key Model Ms (Host Connected Keyboards).

Type 1 "M122s" were perhaps the most conservatively designed Model M keyboards as they almost completely resembled their Model F predecessor. The top cover piece design was virtually identical to the "F122's" from the top and sides, including retaining the Model F-style two-setting riser feet that can be accessed via large grey circular buttons on either side of the keyboard. A way to tell either keyboard apart is the bottom cover piece, which for "F122s" was black painted metal compared to all "M122s'" dyed pearl-white plastic. The usual plastic used on either case piece is likely the same PVC used on other Model Ms of the period, which crucially seems more robust than any Model F Converged Keyboard plastic piece as those were known to experience cracking. Some Type 1s produced by IBM UK were known to yellow^[60][60]
ASK Keyboard Archive - P/N 1389160 (1986, IBM-UK) [accessed 2023-10-23]. License/note: photos saved from volatile eBay Kleinanzeigen listing, photos used under fair dealing.. Type 1 usually connected to its host terminal via a permanently attached grey coiled cable terminating in a 240-degree 5-pin DIN plug with a screwable metal jacket. They exclusively used IBM silver-square badges regardless of generation. Some keyboards for 3270-family terminals may have an 8-position DIP switch bank for setting keyboard ID.

6770/6780 System Movable Keyboard

The IBM 6770 Wheelwriter System (impact printer) and 6780 Quietwriter System (non-impact printer) were a series of unusual follow-ups to the original Wheelwriters 3 and 5 and Quietwriter 7 electronic typewriters with a discrete, movable keyboard. They were first announced in September 1985 and started shipping between October and November of that same year. For both 6770 and 6780, there was a Function Pack 20 (System/20) and Function Pack 40 (System/40) model that had 11,500 or 26,000 user character storage respectively. A System/20 model could be upgraded to System/40 specification after purchase by changing a large rear-mounted cartridge and installing an IBM Textpack A cartridge^[9][9]
IBM - IBM Selectric System/2000 Systems - Wheelwriter/Quietwriter Brief Description of Announcement, Charges, and Availability (#185-109) [accessed 2023-02-26].^[62][62]
IBM - IBM 6770 and 6780 Typing Systems and Associated Options Brief Description of Announcement, Charges, and Availability (#ZG85-0300) [accessed 2023-02-26]..

The keyboard (known as simply the system's "Movable Keyboard") seems to be related to the later keyboard assembly in the IBM 4680 POS Alphanumeric Keyboard as the keyboard's membrane flex cables, backplate size and backplate mounting design match. However, it is unique for having a detachable 80-character LCD cartridge mounted on it and the keyboard sits in a sort of cradle that allows the inner assembly to be adjusted as an alternative to using flip-out feet. The LCD was used for allowing the operator to type lines before printing and for displaying previously typed lines to request corrections^[63][63]
c00kee - IBM "The Edge" - Quietwriter and Wheelwriter System [accessed 2023-02-26].. The rightmost section of the keyboard is largely dedicated to operations to move the current typed-on page and to move through stored characters in memory. The keyboard connects to its host typewriting using a fixed cable with a 6-pin SDL plug but doesn't communicate with any typical IBM keyboard protocol. The connection is a half-duplex bidirectional serial link and its protocol has been documented^[64][64]
D. Given - Reverse engineering the IBM 6770 keyboard [accessed 2023-02-26]..

PC Enhanced Keyboard (1986)

More information: Model M Enhanced Keyboard

eg, P/Ns 1390120, 1390131, 1391401, 42H1292, 42H1292U, UNI041A

The PC-compatible pearl white Enhanced Keyboard is the most well-known and definitive Model M variant, being IBM's premier keyboard design for about a decade following its release. Essentially, if someone says "Model M", they're usually referring to this keyboard. Based on the IBM 7531/7532 Industrial Computer Keyboard design, the first PC-orientated models were released for PC/XT and PC/AT systems in 1986. The following year, the IBM Personal System/2 family of computers helped propel the Model M into stardom and paved the way for the Enhanced Keyboard to become perhaps the most recognisable keyboard of all time. During the 1990s, the PC Enhanced Keyboard gained a significant amount of variants both IBM and non-IBM branded largely thanks to the activities of the then-newly formed Lexmark who made a business out of producing IBM's former designs for other companies. Counting earlier IBM and later Unicomp OEM activities, Enhanced Keyboards branded for the likes of CompuAdd, Dell, General Electric Healthcare, Sabre and Wang are known. A Quiet Touch rubber dome version of the Enhanced Keyboard called the IBM Basic Keyboard was also introduced in 1993. Lexmark and Unicomp themselves also put their brand to the design, calling their keyboards the Lexmark Classic Touch and Unicomp Customizer (later Classic) respectively. The Unicomp Classic remains in production.

Type II 122-key Converged Keyboard (1986)

eg, P/Ns 0985955, 1390238, 1390413, 1390416, 1390572, 1390587, 1390702, 1390713, 1390728, 1390876, 1390886, 1390888, 1390881, 1390891, 1392450, 1397979

The Type 2 122-key Model M was a supplement to the Type 1 "M122" Converged Keyboard, introduced less than a year after them. The Type 2 "M122" was formally introduced in June 1986 with the 3270-family IBM 3191 Model A10 and B10 Display Stations and the 5250-family IBM 3196 Model A10 and B10 Display Stations, which were intended to be "attractively-priced" alternatives to earlier terminals with Model F keyboards such as the IBM 3178 and 5291 Display Stations^[65][65]
IBM - IBM 3191 Display Station Brief Description of Announcement, Charges, and Availability (#186-117) [accessed 2023-01-23].^[66][66]
IBM - IBM 3196 Display Station Brief Description of Announcement, Charges, and Availability (#186-111) [accessed 2023-01-23].. In essence, Type 1 was primarily used for terminals that were largely introduced before "M122s", whereas Type 2 was primarily used for the following generation of terminals introduced after Type 1. In February 1987, Type 2 was utilised with the 5250-family IBM 3197 Model C10 and CD0 Color Display Stations and 3197 Model D10 and DD0 Display Stations^[67][67]
IBM - IBM 3179 Color Display Station C Models Brief Description of Announcement, Charges, and Availability [accessed 2023-03-30].^[68][68]
IBM - IBM 3197 Display Station D Models Brief Description of Announcement, Charges, and Availability (#187-030) [accessed 2023-03-30].. Finally, in March 1988, the Type 2 was again used with the IBM 3206 Display Console^[69][69]
IBM - IBM 3206 Display Console Brief Description of Announcement, Charges, and Availability (#ZG88-0100) [accessed 2023-09-25]..

Type 2 "M122s" were effectively a minor iteration of the Type 1 design, retaining the same overall aesthetic from above but began to migrate away from its Model F origin underneath. They are likewise nicknamed "battleship" or "battleship-sized" keyboards due to their sheer size. Besides the Model M-based FIB Keyboard Controller, "M122s" are in general the largest Model M keyboard designs. Being a Converged Keyboard, they have their recognisable top 24-key and lefthand side 10-key function key banks. The 24 keys typically have either "PFxx" (IBM 3270-style) or "Cmdxx" (IBM 5250-style) nomenclature legends. "M122s" typically used typewriter-style functional layouts, but data entry versions were technically available with IBM Card Punch-style alphanumeric legends.

Type 2 "M122s" remain similar looking to Model F Converged Keyboards and are essentially indistinguishable from the top. The best way to differentiate between Model F and Model M Converged Keyboards is the former's use of a black-painted metal bottom cover piece and the latter's use of a dyed pearl-white bottom cover piece. However, the most notable change from Type 1 to Type 2 granted another way of differentiating them - Type 2 "M122s" abandoned the two-setting riser style feet in favour of 'Model M-style' flip-out feet that can only be adjusted from underneath. As such, Type 2 lacks the large grey circular buttons on both sides that Type 1 retained from its Model F predecessor. The usual plastic used for the cover pieces is believed to be PVC. Type 2 usually connected to their host terminals via a permenately attached grey coiled cable terminating in a 240-degree 5-pin DIN plug with a 90-degree plastic jacket. They exclusively used IBM silver-square badges regardless of generation. Some keyboards for 3270-family terminals may have an 8-position DIP switch bank for setting keyboard ID.

4680 POS Alphanumeric Keyboard (1986)

eg, P/N 76X0035

The IBM 4683 and 4684 were point-of-sale (POS) terminals for the IBM 4680 Store System. The 4683 was first announced in January 1986^[71][71]
IBM - IBM 4683 Point-of-Sale Terminal Model 1 and 2 Brief Description of Announcement, Charges, and Availability (#186-003) [accessed 2023-02-13]. and is known for being IBM's first PC-based POS system, with the 4684 arriving later and differed by being able to function as a terminal controller. The IBM 4680 POS Alphanumeric Keyboard was available for either terminal and is presently the only known buckling spring point-of-sale input device released by IBM. They have a PC/AT-style physical and functional layout and their inner keyboard assemblies match the design of the slightly earlier Model M-based IBM 6770/6780 System Movable Keyboard. The layout makes them a sort of "Model M/AT" if you will. The keyboard sported a double-ended modular cable with 8-pin SDL connectors and communicated in IBM Serial Input/Output (SIO) scancodes via RS485. Inside, they sported a speaker and a Honeywell/Micro Switch V3L-2174-D8 roller lever limit switch for registering key-lock position. This keyboard should not be confused with the SMK-made IBM 4680 Alphanumeric POS (ANPOS) Keyboard released around the same time. The 4680 POS Alphanumeric Keyboard was withdrawn from marketing in April 1992 without a like-for-like replacement and was instead substituted with the aforementioned SMK-made ANPOS Keyboard^[72][72]
IBM - Withdrawal: IBM 4683 and 4684 Point of Sale Terminal Alphanumeric Keyboard (#192-017) [accessed 2023-02-13]..

Space Saving Keyboard (1986)

More information: Model M Space Saving Keyboard

eg, P/Ns 1370475, 1391472, 1392464, 1392934, 1393278, UNI04C6

The Space Saving Keyboards (SSK) are perhaps the most well-known Model M variation over the Enhanced Keyboard. They are a tenkeyless compacted version of said Enhanced Keyboard, first available as a terminal keyboard and later as an option for all or included with some IBM PS/2 computers. Due to the fact numeric keypads were viewed more favourably during the 1980s, the SSKs are relatively rare. Industrial grey versions of the SSKs are known and were popular in the automotive industry during the early 1990s. The SSK exited actual production by 1999, however, Unicomp continued to sell the keyboard into the 2000s using leftover parts from the previous decade. In 2021, the SSK was spiritually succeeded by the Unicomp Mini Model M.

PS/2 50-key Function Keyboard (1987)

eg, P/Ns 1393915, 1392554, 1395249, 1392560

The 50-key Model Ms ("M50s") were matrix-style keypads intended for IBM Personal System/2 computers running bank teller applications. They first appeared in November 1987 for the IBM 8530-R02, a version of the IBM PS/2 Model 30 intended for such a purpose with IBM 4700 host support. They possessed the same physical layout as the 50-key Model F-based IBM 4704 Model 100 keypads and could come with transparent, functional or alphameric legends. This is not accidental as the 50-key Model M was intended to be used with IBM 4700 Personal Computer Application Services, and IBM Consumer Transaction Definition and Consumer Transaction Runtime that allowed IBM PCs to communicate with IBM 4700 controllers^[73][73]
IBM - Customer Announcement Summary - November 3, 1987 (#C87-020) [accessed 2022-09-24].. It is considered an IBM 4700 Financial I/O Device^[74][74]
IBM - IBM Model M50 [accessed 2022-09-24].. Technically speaking, these are the smallest Model Ms capable of featuring an alphameric layout, although the triple segmentation of the keys makes using an "M50" for typing difficult. These are one of two Model Ms whose internal assembly is based on an older Model F device and thus takes several production values from Model F designs; individual barrels, metal keyboard frame, foam padding, and no plastic rivets holding the assembly together. The assembly's previous incarnation was the aforementioned 50-key Model F IBM Model 100s these "M50s" replaced.

Screen Reader Keypad (1988)

More information: Model M Screen Reader Keypad

P/N 1393387

The IBM Screen Reader Keypad ("SRK") was the original peripheral component of the IBM Screen Reader series (PS/2 Screen Reader 1.0, Screen Reader 1.1, Screen Reader/DOS series and Screen Reader/2 series), first announced alongside the original software release in January 1988^[75][75]
IBM - The IBM PC's debut details - The first 10 years [accessed 2022-09-24]..

On introduction, the Screen Reader system brought an increased level of accessibility to PC users with hard or lack of sight. The later Screen Reader/2 was the first fully functional GUI screen reader. The SRK takes the form of an 18-key PS/2-style buckling springs keypad, and it's technically a mouse replacement as it originally plugged into the mouse port of an IBM PS/2 compatible or into a special ISA expansion card for PC/XT and PC/AT style systems that lacked a PS/2 mouse port^[76][76]
IBM - IBM Screen Reader/2 Brief Description of Announcement, Charges, and Availability (#292-363) [accessed 2023-03-07].. As such, the SRK doesn't output standard scancodes and thus will exhibit weird behaviour through a modern PS/2 keyboard port or PS/2 to USB converter. Along with the IBM Model M PS/2 50-key Function Keyboard, the SRK is unique amongst Model Ms in that its internal assembly was based on an earlier Model F keypad assembly and thus took several production values from Model F designs. This included the use of individual barrels, a metal barrel plate, foam padding, and no plastic rivets holding the assembly together. The assembly's previous incarnation was the 24/25-key Model F keypad. The SRK was withdrawn from marketing on 11th April 1995^[77][77]
IBM - Withdrawal: IBM Screen Reader Keypad and Cable -- Replacement Available (#195-112) [accessed 2023-03-08]..

Type III 122-key Converged Keyboard (1989)

eg, P/Ns 58.003, 1394099, 1394100, 1394103, 1394104, 1394114, 1394119, 1394167, 1394308, 1394312, 1394317, 1394320, 1394324, 1394625, 1394801, 1395660, 1395661, 1395662, 1395663, 1397953, 35G4751, 92G9006, 301-5522-01, A218331, CL40356, CLI0356, PRAJ352

The Type 3 122-key Model M was a complete stylistic revamp of the IBM Converged Keyboard design, finally diverging from the design language of the 104-key and 122-key Model F Converged Keyboards. The Type 3 "M122" was introduced exclusively for the IBM InfoWindow series of terminals, which unified the formerly separate IBM 3270 and 5250 terminal families under one branding. The first two were the IBM InfoWindow 3471 (3270-family) and 3476 (5250-family) Display Stations that were made available in June 1989^[82][82]
IBM - IBM InfoWindow 3471 Display Station Brief Description of Announcement, Charges, and Availability (#189-096) [accessed 2023-01-23].^[83][83]
IBM - IBM InfoWindow 3476 Display Station Brief Description of Announcement, Charges, and Availability (#189-097) [accessed 2023-01-23].. They were joined by the InfoWindows 3472 (3270) and 3477 (5250) in September 1989^[84][84]
IBM - IBM InfoWindow 3472 Brief Description of Announcement, Charges, and Availability (#189-132) [accessed 2023-09-25].^[85][85]
IBM - IBM InfoWindow 3477 Brief Description of Announcement, Charges, and Availability (#189-131) [accessed 2023-09-25].. The InfoWindow series was replaced by the InfoWindow II series from 1992 onwards with the 3481 (3270, September 1992), 3482 (3270, September 1992)^[86][86]
IBM - IBM InfoWindow II 3481/3482 Display Station Brief Description of Announcement, Charges, and Availability (#192-237) [accessed 2023-01-23]., 3483 (3270), 3486 (5250, September 1992) and 3487 (5250, September 1992)^[87][87]
IBM - IBM InfoWindow II 3486/3487 Display Station Brief Description of Announcement, Charges, and Availability (#192-192) [accessed 2023-01-23]., and the InfoWindow Modular Display Stations 3488 (5250, September 1992^[88][88]
IBM - IBM InfoWindow II 3488 Modular Display Station Brief Description of Announcement, Charges, and Availability (#192-193) [accessed 2023-09-25].) and 3489 (5250, October 1994^[89][89]
IBM - IBM InfoWindow II 3489 Modular Display Station Model V Announcement (#194-309) [accessed 2023-09-25].). Type 3 remains in production today as the Unicomp Terminal 122 series, produced for individual purposes and third-party terminal and thin client brands such as Decision Data, ComputerLab International, I-O Corporation, NLynx Technologies and Praim.

Type 3 "M122s" took the Converged Keyboard family in a new direction, radically overhauling the "battleship" design from the Model F era heldover by Type 1 and 2 "M122s" and infusing styling cues from the IBM Enhanced Keyboard into it. The design was slightly compacted and made lighter; as such, they're typically referred to as a "battlecruiser" or "battlecruiser-sized" keyboard by enthusiasts to differentiate them from their older and larger counterparts. Being a Converged Keyboard, they have their recognisable top 24-key and lefthand side 10-key function key banks. The legends on the 24-key bank were simplified to a "Fxx" nomenclature for 3270 or 5250-style keyboards where both previously had their own unique format. "M122s" typically used typewriter-style functional layouts, but data entry versions were technically available with IBM Card Punch-style alphanumeric legends.

Type 3 "M122s" are very easy to distinguish from both previous types thanks to their use of the distinct Model M wedge shape profile, oval-shaped IBM branding instead of square-shaped, slimmer bezels between the keys and the side edges, a smaller surface area around the 24-key bank's raised platform, and a three-way cable router on the bottom cover. Type 3s were made of PVC during the IBM days^[90][90]
krazy-bunny-gal @ eBay - VINTAGE IBM 1394324 Terminal Keyboard - 1995 [Buckling Spring] [accessed 2022-12-31]. License/note: retrieved via Wayback Machine (2022-12-31 capture)., but Unicomp has since switched to using PC+ABS. Unicomp also introduced raven black-coloured versions of the Type 3, further distinguishing these from past "M122s". Type 3s have a permanently attached and typically coiled cable but its coils are smaller and the cable is thinner than on previous types (more suited to fit the aforementioned cable router), and for IBM-branded versions, the DIN plug is replaced with an 8-pin modular plug (the same physical plug used for ethernet and RJ-45 purposes). Despite that change, Type 3s continued using IBM scancode set 3 for communication, so only a physical change to connectivity was made. Unicomp-made versions that aren't IBM branded could change both the cable and plug style to suit their customer's needs, as such, Type 3 "M122s" with AT-style DIN plugs and non-coiled cables have been documented. Type 3 abandoned support for DIP switches, so not even a recess and blanking plate are present for them. Due to shared design and moulds, some Type 3s may have a visible area where lock-light LEDs would be present for the slightly later Type 4 (though some lack this altogether). Type 3s were also the first "M122" type to have Quiet Touch rubber dome alternatives to buckling springs, which had limited availability during the IBM/Lexmark era but saw wider adoption by Unicomp.

Type IV 122-key Host Connected Keyboard (1990)

eg, P/Ns 58.069, 1369969, 1369986, 1396901, 1396902, 1396908, 1396910, 1396911, 1396914, 1396990, 1397000, 1397003, 1397024, 1397506, 1397507, 1397513, 901022-50, AC40956, AC40T56, ACP2956, BO40B56, BO40B5A, DCI0852, DD43T56, UB40B5A, UB40L5A, UB40T56, UN40L5A, UNI0852, UNI3B5A

Officially the IBM Personal System/2 Host Connected Keyboard, the Type 4 122-key Model M was a variant of the Type 3 Converged Keyboard intended for terminal emulation on IBM PS/2 personal computers. It wasn't designed with a specific PS/2 model in mind, instead, it was available as an option for any IBM PS/2 or later series model that qualified for IBM's Select-A-Keyboard scheme. Select-A-Keyboard allowed customers to choose from a variety of keyboards for their qualifying system at the time of purchase for no additional charge. Select-A-Keyboard and the PS/2 Host Connected Keyboard were both announced in June 1991^[92][92]
IBM - IBM Personal Systems Technical Solutions Issue 4, 1991 (#G325-5013-00) [accessed 2023-10-10]. License/note: document archived by Ardent Tool. but production of these keyboards started at least a year earlier. Lexmark later produced its own self-branded version. Type 4 remains in production today as the Unicomp Emulator 122 (continuation of the professional host-connected keyboard) and PC 122 (a more consumer-orientated keyboard), produced under their own branding or for third-party thin client brands such as 10ZiG Technology, Affirmative Computer Products, BOS/BOScom, Development Concepts, Inc., I-O Corporation and NLynx Technologies.

Type 4 "M122s" are at their core just a specialised version of the Type 3 Converged Keyboard with PC compatibility, so it's considered a terminal emulator keyboard rather than simply a terminal keyboard that most of its predecessors were. The keyboard's design is for the most part identical and is still considered a "battlecruiser" or "battlecruiser-sized" keyboard by enthusiasts. But to reflect their nature as a dual-purpose keyboard, Type 4s also have at least two-colour dye-sublimated legends to differentiate PC-only functions (usually in blue) and terminal/universal functions (in black). Being a Converged Keyboard at their core, they have their recognisable top 24-key and lefthand side 10-key function key banks. The legends on the 24-key bank were generally "Fxx" nomenclature for 3270 or 5250-style keyboards. IBM and Lexmark branded variants were always intended for IBM 3270 emulation, but 5250-orientated versions are known for third-party branded Type 4s. All Type 4 "M122s" currently discovered use a typewriter-style layout with no data entry style version yet found.

The best way to tell IBM-branded Type 3s and 4s apart is the latter's presence of lock-light LEDs in the top-right corner of the keyboard. Unicomp-made keyboards can have or lack these lights though, so in such cases, the two-colour legends on the keycaps can also be used to differentiate them. Like Type 3s, they have the distinct Model M wedge shape profile, (originally) oval-shaped IBM branding, slim bezels between the keys and the side edges, a small surface area around the 24-key bank's raised platform, and a three-way cable router on the bottom cover (though many Type 4 cables don't fit the longer channels). Type 4 "M122s" originally ditched attached cables in favour of removable SDL to PS/2 cables that IBM Enhanced and Space Saving Keyboards famously used. Unicomp later supplemented and replaced them with attached cables terminating in an AT-style DIN, PS/2 or Type-A USB plug. Type 4s were made of PVC during the IBM days, but Unicomp has since switched to using PC+ABS. Unicomp also introduced raven black-coloured versions of the Type 4, which today is now the standard option. Like Type 3, Type 4 "M122s" never had the DIP switches some of their predecessors could have. Quiet Touch rubber dome versions of Type 4 have been available since Unicomp took over production.

M1/M2 Selectric Touch Keyboard (1990)

eg, P/Ns 1395300, 1398419, 25H2142, 42H0468, 60G3570

The Model M1s and M2s were lightweight alternatives to the Enhanced Keyboard. Whilst they mostly used the same buckling spring actuators as their brethren, almost everything else about the design was changed as they have no metal base plate, an integrated front cover and keyboard frame, and a completely different logic board featuring surface-mounted components. The M1/M2 physical design was patented in October 1989 as USD330199S^[95][95]
Lexmark - Keyboard [accessed 2022-05-29]. and the earliest production examples seen are from 1990^[96][96]
Tha_Pig - Free IBM model M2 buckling spring keyboard [accessed 2022-05-29].. The difference between the M1s and M2s is that the M1 was sold as a standalone product under the "Easy OPTIONS by IBM" brand and the M2 was bundled with full computer systems (usually, IBM Personal System/1 series of low-end home computers). Otherwise, M1s and M2s are the same keyboards. An IBM 3153 terminal and a "bordered" IBM EduQuest variant of the M2 also existed, as well as Quiet Touch rubber dome versions. Despite the name, these keyboards have no relation to the IBM Selectric electric typewriters. Lexmark's self-branded versions were marketed as the Easy Touch (Quiet Touch) and Streamlined (buckling spring) Keyboards^[97][97]
clickykeyboards - history/scanned images of Lexmark International, Inc keyboard brochure (1993) [accessed 2023-07-02]. License/note: photos used under fair dealing..

M3 Numeric Keypad & Laptop Keyboard Assembly (1991)

More information: Model M3 PS/2 L40SX Numeric Keypad

eg, P/Ns 1396130, 1396199

The Model M3 family was the first major deviation from the expected buckling-spring keyboard of a Model M-designated keyboard such as everything that came before. The M3 keyboard assembly was introduced with the IBM 8543 Personal System/2 L40SX in March 1991^[32][32]
IBM - THE IBM PS/2 MODEL L40 SX SYSTEM AND FEATURES (#191-030) [accessed 2022-01-18]., which was an early IBM notebook that featured IBM's first buckling [rubber] sleeve based keyboard of any kind. An optional external numeric keypad with a PS/2 mouse passthrough port was also available for the L40SX that for US-produced examples carried the "M3" designation. The M3 keyboard and numeric keypad assemblies were repackaged to become the Model M4 family desktop peripherals in 1991. M3 was spiritually succeeded by the Model M6 family in 1992.

M4/M4-1 Space Saver Keyboard & Numeric Keypad (1991)

More information: Model M4 & M4-1 Space Saver Keyboard & Numeric Keypad

eg, P/Ns 1397451, 1397901, 1379590, 84G2524, 84G2526

The Model M4s were the discrete desktop and server environment adaptations of the L40SX keyboard and numeric keypad Model M3 assemblies. The M4's physical design was patented in December 1991 as USD344724S^[100][100]
Lexmark - Keyboard [accessed 2022-05-29]. and production began immediately. The M4 is a straight adaptation of the L40SX assembly, featuring a PS/2-based controller. The M4-1 on the other hand adds a TrackPoint II pointing stick module, making it the first IBM keyboard with a TrackPoint. All M4s use the same buckling rubber sleeve switches as their M3 predecessors. M4s were originally produced by Lexmark then Key Tronic after April 1996, but Unicomp continued production until the late 2000s as the Unicomp Mighty Mouse keyboards. A companion Model M4 or M4-1 numeric keypad was available for all M4s.

M5-1 16mm Trackball Keyboard (1992)

eg, P/N 1370478

The Model M5-1 was one of two variants of the Enhanced Keyboard with integrated trackball modules introduced at the same time by February 1992^[102][102]
PC Mag - 25 Feb 1992 [accessed 2022-01-22].. The M5-1 features 16mm trackball, two standard-click mouse buttons and two stepped-click mouse buttons that act as if the user is holding down a mouse button with a single press to help with highlighting and scrolling with the trackball, all in a protruding module surrounding the arrow keys. The keyboard is otherwise a standard SDL-based third generation Enhanced Keyboard of the period. The M5-1 was exclusively made by Lexmark and didn't continue production for long.

M5-2 25mm Trackball Keyboard (1992)

eg, P/Ns 1398150, 59G7982, 59G9757, 92G7455

The Model M5-2 was one of two variants of the Enhanced Keyboard with integrated trackball modules introduced at the same time by February 1992^[102][102]
PC Mag - 25 Feb 1992 [accessed 2022-01-22].. The M5-2 features 25mm trackball, two standard-click mouse buttons and two stepped-click mouse buttons that act as if the user is holding down a mouse button with a single press to help with highlighting and scrolling with the trackball, all in a protruding module placed above the LED lock-light section of the keyboard. The keyboard is otherwise a standard Enhanced Keyboard style Model M from whatever generation was current at the time of a given example's production. Unlike the M5-1, the M5-2 continued in production until relatively recently via Unicomp; first branded as the Unicomp On-The-Ball and later the Unicomp Classic Trackball. The Lexmark era models specifically were the last Model M variant released that featured modular SDL connection. Unicomp has since moved to using fixed cables for them just like their other keyboards.

M6 ThinkPad Keyboard Assembly (1992)

More information: Model M6 & M6-1 ThinkPad Laptop Keyboard Assemblies

eg, P/Ns 1397800, 1399300, 44G3618, 44G3620, 59G7569

The Model M6 was a range of IBM and Lexmark portable computer keyboards that first appeared with the IBM 8554 PS/2 CL57SX notebook in late February 1992^[104][104]
Ardent Tool - IBM PS/2 Model CL57 SX System 8554-A45 and Features Announcement Letter (#ZG92-0165) [accessed 2023-07-13].. Together with its closely related successor, M6-1, the M6 family was IBM's premier laptop keyboard assembly design for the following 3 years. For all intents and purposes, M6 was the original true IBM ThinkPad keyboard, which established its identity with the IBM 9552 ThinkPad 700 and PS/55note C52 in October 1992^[105][105]
ThinkWiki - ThinkPad History [accessed 2021-11-18]. as the first [IBM] strain gauge TrackPoint keyboard of any kind and popularised IBM's classic 7-row keyboard layout. At its core, the M6 was a refined Model M3 keyboard assembly from the IBM 8543 PS/2 L40SX and indeed the original M6s (referred to as "Type One", for the CL57SX) shared the same physical layout with M3. But whilst still using IBM buckling sleeves keyswitches, the dual clip keycap mount system with plunger rod actuation M3 (and M4 and M4-1) used was replaced with barrel-fixed slider system that made the keycaps easier to remove and replace. M6s used a brown coloured slider. M6s would see two more subsequent types that further refined the layout; Type II for the 2141 PS/note 182 series introduced the 7-row layout to M6 but kept using the square secondary keys, and Type III for the ThinkPads 700 and 720 that reduced the depth of the secondary keys to give M6 the appearance of the classic ThinkPad style keyboard used for many years after. Besides the already mentioned laptops, IBM also used M6s for the 5527 PS/55note N27sx (Type I) and 2618 ThinkPad 350 and PS/note 425 (both Type II). Lexmark, who produced most M6s, also used related keyboard assembly designs for its OEM series laptops such as the AR10 and GS20 (both Type II) with a integrated 16mm trackball or FSR pointing stick respectively. Lexmark self-branded AR10 and GS20 as Lexbook laptops, but also produced them for other comapnies such as CompuAdd, Cube Computers and Hyundai. M6 was succeeded by M6-1 the following year and long before Lexmark exited keyboard manufacturing in 1996, so only Lexmark-made and some early IBM U.S. produced examples are known.

M6-1 ThinkPad Keyboard Assembly (1993)

More information: Model M6 & M6-1 ThinkPad Laptop Keyboard Assemblies

eg, P/Ns 1403740, 232011-001, 29H8109, 29H8797, 39H4046, 42H3979, 66G0120, 84G5728

The Model M6-1 was a range of IBM and Lexmark portable computer keyboards, developed as a slightly revised follow-up to the original M6. They first appeared in June 1993^[106][106]
IBM - IBM ThinkPad 500 Brief Description of Announcement, Charges, and Availability (#193-167) [accessed 2023-05-12]. with the IBM 2603 ThinkPad 500 series. Like its predecessor, M6-1's lineage is with Model M3-bearing IBM 8543 PS/2 L40SX, it uses IBM buckling sleeve keyswitches with barrel sliders and easily removable keycaps instead of the dual-clip retention M3s (and M4s and M4-1s) used. For the most part, M6-1s use TrackPoint II pointing sticks as well. Whilst the difference between M6 and M6-1 isn't clearly defined in official text, one observed difference between IBM-branded keyboard assemblies designated "M6" and "M6-1" was their use of brown or black coloured barrel sliders respectively. M6-1 also has several new form-factor/layout combinations. The first M6-1 based keyboard assemblies used by the ThinkPad 500 and its 2604 ThinkPad 510Cs successor are referred to as Type IV, which was a compact 6-row layout design that attempted to fit as many keys as possible into the width of a 60% style keyboard. All keys are slightly smaller than usual unit sizes, and smaller IBM buckling sleeve gauges are used to match. The most familiar and iconic M6-1 is Type V, which was introduced with the IBM 9545 family (ThinkPads 750 series, 755C series and 370C) in September 1993 as an evolution of the original Type III Model M6. Type V M6-1 is like Type III M6 in that it's a familiar 7-row classic ThinkPad style layout keyboard assembly for the flagship ThinkPad series, but Type V adds an Fn key and an outer frame that allowed the keyboard to act as a hinged module. Type Vs can be lifted like a car's bonnet (or hood in US English) to access the host's main system components. Type Vs can vary based on the shape and function of their mouse buttons. Finally, the Type VI is a completely non-IBM-branded design from Lexmark for OEM partners Winbook Computer Corporation and AST Research Inc. on their XP series and 900N series notebooks respectively. They first appeared on Winbook laptops around May 1994. Type VI is another 6-row design, but unlike Type V, the keycaps are returned to normal scaling like to other M6-1s. Whilst some Type VIs used IBM TrackPoint IIs, others used Lexmark's FSR pointing stick instead. In addition to the three new types, M6-1s were also produced to Type III expected traits for Tadpole laptops such as the SPARCbook 3 series, P1000 series, ALPHAbook 1, SPARCbook 3000 series and the related IBM RS/6000 Notebook N40, though uniquely with an added third mouse button. Other IBM portable computers or workstations that used M6-1s include the 2619 ThinkPad 355, 2620 ThinkPad 360, 2625 ThinkPad 365, 6042 ThinkPad Power Series 850 and 7249 RS/6000 Notebook 860 (all Type V). Some of the later IBM M6-1 hosts also used TrackPoint III instead of II. Like with M6, Lexmark also used M6-1s for their own products including the Lexbooks MB10, MB15 and SE10; all of which used a Type IV derived design with a Lexmark-specific Mouse Key pointing device. Lexmark produced the majority of M6-1s, though due to Lexmark's exit from the keyboard market, Key Tronic took over production. This change in OEM only resulted in slight cosmetic changes. By the late 1990s, IBM moved to various scissor-switch keyboards for its ThinkPads that whilst in many cases visually identical to M6-1 were not Model M-designated. The latest year for an M6-1 to be produced observed thus far was 1999^[107][107]
TheMK - A NOS IBM Model M6-1 ThinkPad 365 Keyboard Assembly [accessed 2022-10-27]..

M7 50-Key RPOS MSR Keyboard (1993)

More information: Model M7, M7-1, M8, M9 & M11 Retail POS Keyboards#M7

eg, P/Ns 92F6320, 41J7248, 7431818

The Model M7 is a 50-key point of sale keyboard with an integrated magnetic stripe card reader in the Retail POS (RPOS) series of IBM buckling rubber sleeve POS input devices. The M7 was originally known as the IBM Retail POS Keyboard with Card Reader. Its earliest host system was the IBM 4694 POS Terminal Model 001 announced in June 1993^[108][108]
IBM - IBM 4694 POS Terminal Model 001 Brief Description of Announcement, Charges, and Availability (#193-150) [accessed 2022-05-29]. and it was a successor to the IBM 4680 series 50-Key Modifiable Layout Keyboard. For the most part, the layout and function of the M7 are customisable and the keypad has many transparent keytops to facilitate printed or written legends on paper. However, almost all M7s have a dedicated numeric keypad in the middle key bank and a "Ctrl" key in the top-left. The M7 was replaced by the "Model M-e" Modular 67-Key POS Keyboard in 2008, although production was believed to be continued by TGCS until 2015.

M7-1 50-Key RPOS Keyboard (1993)

More information: Model M7, M7-1, M8, M9 & M11 Retail POS Keyboards#M7-1

eg, P/Ns 92F6310, 41J7247

The Model M7-1 is a 50-key point of sale keyboard without an integrated magnetic stripe card reader in the Retail POS (RPOS) series of IBM buckling rubber sleeve POS input devices. The M7-1 was originally known as the IBM Retail POS Keyboard. Its earliest host system was the IBM 4694 POS Terminal Model 001 announced in June 1993^[108][108]
IBM - IBM 4694 POS Terminal Model 001 Brief Description of Announcement, Charges, and Availability (#193-150) [accessed 2022-05-29]. and it was a successor to the IBM 4680 series 50-Key Modifiable Layout Keyboard. For the most part, the layout and function of the M7-1 are customisable and the keypad has many transparent keytops to facilitate printed or written legends on paper. However, almost all M7-1s have a dedicated numeric keypad in the middle key bank and a "Ctrl" key in the top-left. The M7-1 was replaced by the "Model M-e" Modular 67-Key POS Keyboard in 2008.

M8 50-Key RPOS LCD Keyboard (1993)

More information: Model M7, M7-1, M8, M9 & M11 Retail POS Keyboards#M8

eg, P/Ns 92F6330, 41J7250, 44D1890, 7431822

The Model M8 is a 50-key point of sale keyboard with a tilt-adjustable 2x20 LCD screen and integrated magnetic stripe card reader in the Retail POS (RPOS) series of IBM buckling rubber sleeve POS input devices. The M8 was originally known as the IBM Retail POS Keyboard with Card Reader and Display. Its earliest host system was the IBM 4694 POS Terminal Model 001 announced in June 1993^[108][108]
IBM - IBM 4694 POS Terminal Model 001 Brief Description of Announcement, Charges, and Availability (#193-150) [accessed 2022-05-29]. and it was a successor to the IBM 4680 series 50-Key Modifiable Layout Keyboard and Operator Display (also known as the IBM 4680 Combined Keyboard/Display). For the most part and just like the M7s, the layout and function of the M8 are customisable and the keypad has many transparent keytops to facilitate printed or written legends on paper. However, almost all M8s have a dedicated numeric keypad in the middle key bank and a "Ctrl" key in the bottom-left. The M8 was replaced by the "Model M-e" Modular 67-Key POS LCD Keyboard in 2011, although production was believed to be continued by TGCS until 2015.

M9 RANPOS Keyboard (1993)

More information: Model M7, M7-1, M8, M9 & M11 Retail POS Keyboards#M9

eg, P/Ns 92F6271, 7431724

The Model M9 is a 116 (US English) or 117 (rest of world) key alphanumeric point of sale (ANPOS) keyboard with an integrated magnetic stripe card reader in the Retail POS (RPOS) series of IBM buckling rubber sleeve POS input devices. The M9 was originally known as the IBM Retail ANPOS Keyboard with Card Reader. Its earliest host system was the IBM 4694 POS Terminal Model 001 announced in June 1993^[108][108]
IBM - IBM 4694 POS Terminal Model 001 Brief Description of Announcement, Charges, and Availability (#193-150) [accessed 2022-05-29]. and it was a successor to the IBM 4680 series ANPOS Keyboard. The M9's name is usually abbreviated as simply ANPOS, but it's also known as RANPOS (Retail ANPOS) or NANPOS ("New" ANPOS) to differentiate it from earlier keyboards of the same name. The keyboard has two distinct types of keys - the 60%-size alphanumeric standard keys and the transparent keytop keys all RPOS keyboards use. Like its siblings, M9 has a dedicated numeric keypad within the transparent-topped keys but enough spacing between it and the alphanumeric keys is given to allow for a full Enhanced layout configuration. The M9 was ultimately replaced by the "Model M-e" MANPOS Keyboard in 2008, although production was believed to be continued by TGCS until 2015.

M11 RPOS Modifiable Layout Keyboard (1993)

More information: Model M7, M7-1, M8, M9 & M11 Retail POS Keyboards#M11

eg, P/Ns 92F6290, 41J8019

The Model M11 is a 133-key point of sale ortholinear/matrix keyboard with an integrated magnetic stripe card reader in the Retail POS (RPOS) series of IBM buckling rubber sleeve POS input devices. The M11 was originally known as the IBM Modifiable Layout Keyboard. Its earliest host system was the IBM 4694 POS Terminal Model 001 announced in June 1993^[108][108]
IBM - IBM 4694 POS Terminal Model 001 Brief Description of Announcement, Charges, and Availability (#193-150) [accessed 2022-05-29]. and it was a successor to the IBM 4680 series Matrix Keyboard. Sometimes described as a "key array", the M11 is essentially an adaptation of the M9 design where almost every key is relegendable. The only exception is the dedicated numeric keypad that all its RPOS siblings have. These could be configured with an alphanumeric layout, an entirely functional layout or a mix of alphanumeric and functional. Unlike the rest of RPOS, the M11 never received a like-for-like Modular POS replacement but an M11 can theoretically be substituted with two "Model M-e" Modular 67-Key POS Keyboards.

M13 Pointing Stick Keyboard (1993)

More information: Model M13 TrackPoint II Keyboard

eg, P/Ns 13H6705, 1403380, 18P7970, 82G3281, 92G7461

The Model M13 was a variant of the Enhanced Keyboard with an (at first) integrated TrackPoint II strain gauge-based pointing stick. They first appeared in Lexmark advertising sometime between May and November 1993^[110][110]
PC Mag - 1993-05-25 [accessed 2022-05-29].^[111][111]
PC Mag - 1993-11-23 [accessed 2022-05-29]. with major production observed from the following year. The M13 in a similar fashion to the SSK is one of the most well-known Model M variants and the black version is well sought after. M13s could also come with a PS/2 mouse pass-through port for mice on the back and have noticeably stronger cover set texturing compared to almost every other Model M. After Lexmark and Maxi Switch quit production, Unicomp continued producing and marketing the M13 from December 1998^[112][112]
Unicomp - Enhanced Quiet Touch with Pointing Stick [accessed 2022-10-03]. License/note: retrieved via Wayback Machine (1998-12-06 capture). until June 2007^[113][113]
Unicomp - On-The-Stick [accessed 2022-10-03]. License/note: retrieved via Wayback Machine (2007-06-01 capture)., branding the keyboard as the Unicomp On-The-Stick and using their unique force-sensing resistor based pointing stick.

M15 Select-Ease Keyboard (1994)

P/Ns 1378300, 13H6689 & 1428401

The Model M15 was a highly adjustable ergonomic tenkeyless-like keyboard based on the Model M1/M2 design and was branded as either the IBM Adjustable Keyboard, OPTIONS by IBM Adjustable Keyboard, or Lexmark Select-Ease Keyboard. Being the only ergonomic keyboard as per today's standards that IBM ever marketed, the Model M15 features a high degree of customisability; including split, tilt, swivel and tenting capabilities. For convenience, the arrow keys are duplicated on both halves of the keyboard and the split spacebar has an Erase-Eaze feature. They can act as hosts to an M15 numeric keypad seen below. They are candidates for the last IBM-sanctioned buckling springs keyboard design.

M15 Numeric Keypad Option (1994)

P/N 1403599

The Model M15 numeric keypad was an optional accompaniment to M15 Select-Ease Keyboards that connected to said keyboards via a proprietary connection. They too based on the Model M1/M2 design, but only one part number is known - P/N 1403599 - that is shared for both IBM and Lexmark branded M15 keyboards. They have four flip-out feet to allow the user to match the profile of a host M15 keyboard and its adjustable ergonomic feet. They are the smallest official IBM buckling springs device currently known.

5576-C01 TrackPoint II Japanese Keyboard (1994)

More information: IBM Japan 5576-C01 TrackPoint Keyboard and its Unicomp descendants

P/Ns 66G8362, 66G8363

The IBM 5576-C01 TrackPoint II Japanese Keyboard was a Japanese-only Model M offshoot produced solely for the IBM PS/55E all-in-one computer. These are known for featuring a highly unique rotating vertical stand that allows you to park the keyboards upwards on its back wall. These use TrackPoint II like its larger Lexmark or Maxi Switch produced Model M13 siblings. They could also come in proprietary combined signal PS/2-like cable (P/N 66G8363) or a more standard Y-split keyboard and mouse PS/2 cable (P/N 66G8362). It is a candidate for the last IBM-sanctioned buckling springs keyboard design.

M6-1 Apple Newton MessagePad Keyboard (1996)

More information: Apple Newton Keyboard - The time Apple turned to IBM/Lexmark for a Model M

P/Ns 661-0963, B661-0963, D661-0963, F661-0963 & S661-0963

The Apple Newton was a series of personal digital assistants first released in August 1993^[116][116]
D. Luckie - Newton MessagePad [accessed 2022-10-27]. License/note: retrieved via Wayback Machine (2014-02-26 capture). that was regarded as ahead of its time but let down by its "high price and early problems with its handwriting recognition feature" and eventually axed by Steve Jobs upon his return to Apple. Perhaps due to the latter issue, Apple made a physical keyboard available - model X0044 - upon the release of Newton OS 2.0 in early 1996^[117][117]
InfoWorld - 1996-01-22 [accessed 2022-10-27].. Unbeknownst to many, Lexmark was behind the keyboard's design, which was based on the keyboard assemblies used on the IBM ThinkPads 500 and 510 and Lexmark Lexbooks MB-10, MB-15 and SE-10. This makes X0044 a derivative of the Model M6-1 and allows for the sole instance of an Apple-branded Model M-family keyboard. Due to the time of introduction towards the end of Lexmark's keyboard production activities, it is believed Key Tronic manufactured most of these.

Industrial M13 Pointing Stick Keyboard (1996)

More information: Model M13 TrackPoint II Keyboard#Industrial

P/N 06H4173

As with Enhanced Keyboards and Space Saving Keyboards, the Model M13 also had an industrial counterpart sporting a slightly olive-tinted grey cover set designed to obscure dirt and damage inflicted in an industrial environment. The changes are purely cosmetic though as these are electrically identical to its pearl white and raven black counterparts. The industrial M13 seemed to be introduced after Lexmark stopped manufacturing keyboards, so the earliest examples were manufactured by Maxi Switch and use TrackPoint II strain gauge pointing sticks. At some point during 1996, production was passed to Unicomp and the TrackPoint II stick was swapped for an FSR stick. The sole part number known is 06H4173 and its full production timeline is unclear.

Unicomp On-The-Ball Plus (2000)

More information: Model M13 TrackPoint II Keyboard#OTBP

eg, P/N UNI0496

The Unicomp On-The-Ball Plus was a special multi-pointing device keyboard that sold for only a relatively short time in the 2000s. It's essentially a merger of the Models M5-2 (On-The-Ball) and M13 (On-The-Stick) designs. It first appeared on Unicomp's website in January 2000 and was marketed as being a keyboard that could be "convienent for all users"^[118][118]
Unicomp - On The Ball Plus 101 [accessed 2022-09-30]. License/note: retrieved via Wayback Machine (2000-01-15 capture).. The trackball module was the same 25mm module used on Model M5-2s, however as expected, the pointing stick was Unicomp's signature FSR-based pointing stick also found on their other pointing stick keyboards.

Unicomp EnduraPro (2000)

eg, P/Ns UB204G6, UB404G6, UB40PGA, UNI0PGA, XR4R4G6

The EnduraPro is Unicomp's spiritual successor to the Model M13 and was their first self-introduced Model M variant. The EnduraPro is an adaptation of the IBM 5576-C01 tooling and thus both closely resemble each other. However, the vertical stand feature has been removed and the TrackPoint II pointing stick has been swapped out for Unicomp's own force-sensing resistor based implementation. Unicomp's typical layout options are also available. After two decades of production with the same tooling, the moulds used to produce them are prone to producing defects.

"M-e" 4820 32-Key POS Keypad (2000)

eg, P/N 40N6377

The monitor-mounted IBM SurePoint 4820 Keypad was the first of the Model M "extended family" ("M-e") POS input devices, an undesignated extension of the Model M Retail POS keyboard family (Models M7 through M11) introduced by September 2000. This 32-key keypad was the smallest member of the "M-e" family typically mounted on the right side of various IBM SurePoint POS touchscreen monitors, and is considered to be a part of the pre-Modular (Pre-MPOS) series. In its default layout, 31 of the 32 keys are individually discrete, typically featuring a numeric keypad with a zero key taking up two key positions (hence 31) and a Ctrl key on the lower 4x4 key bank. Examples with or without an integrated magnetic stripe reader are known. Like the RPOS family this keypad extends from, it uses IBM bucking rubber sleeves keyswitches.

"M-e" PS/2 ANPOS Keyboard (2001)

eg, P/Ns 13G2127, 13G2130, 10J0793, 10J0902, 14J0601

The IBM PS/2 ANPOS Keyboard with Integrated Pointing Device was a "Model M-e" enhancement of the Model M9 RANPOS Keyboard design and a part of the pre-Modular (pre-MPOS) series, thus occasionally referred to as the M9-e in fan circles. For the most part, the M9 and M9-e are virtually identical save the integrated force-sensing capacitor based Synaptics TouchStyk pointing stick referred to as simply "POS pointer" in marketing. As such, it too has two distinct types of keys, an integrated magnetic stripe reader, and was available in 116-key (US English) and 117-key (rest of world) layouts. It also uses IBM bucking rubber sleeves keyswitches.

"M-e" CANPOS Keyboard (2002)

eg, P/Ns 44D1860, 54P8779, 54P8786

The IBM Compact ANPOS (CANPOS) Keyboard was the first wholly new and most notable "Model M-e" keyboard design introduced in 2002 and a part of the pre-Modular (pre-MPOS) series. CANPOS fits a full-size keyboard with many programmable keys in a chassis that is a similar width to a tenkeyless keyboard. In total, CANPOS Keyboards have 133 (US English) or 134 (rest of world) keys. Additionally, all alphanumeric keys are slightly thinner compared to their M9 RANPOS, M-e PS/2 ANPOS and later M-e MANPOS counterparts. CANPOS lacked any sort of key lock but had a fixed magnetic stripe reader and force-sensing capacitor based Synaptics TouchStyk pointing stick. Once again, it also uses IBM bucking rubber sleeves keyswitches. CANPOS was succeeded by IBM Modular CANPOS (MCANPOS, aka CANPOS II) in 2008.

Unicomp SpaceSaver/Ultra Classic (2007)

eg, P/Ns UB40P36, UB40P3A, UB40P46, UB40P4A, UB4ZPHA, UN40PSA, UNI0P46, UWZBP4A

The Ultra Classic (also known as the SpaceSaver M for the Mac version and previously called SpaceSaver itself) was Unicomp's sole save-saving no-frills alternative to the Unicomp Classic before the introduction of the New M and Mini M. It is a sibling to the Unicomp EnduraPro as it is made with the tooling formerly used to produce IBM 5576-C01 keyboards. Unlike the EnduraPro, these do not have an integrated pointing stick. However, like the EnduraPro, the moulds used to produce them are old and are producing defects.

"M-e" 4613 96-Key POS Keyboard (2008)

P/N 44D4035

The IBM 4613 SurePOS 100 Express System was a compact all-in-one POS terminal introduced in 2008 that featured an integrated IBM buckling rubber sleeves based keyboard assembly. The keyboard itself resembles a shortened IBM Model M11 and in fact takes production values from late-era RPOS keyboards and sports an RPOS-style magnetic stripe reader. It has 96 keys in an ortholinear layout with both relegendable and alphanumeric setups known. It is considered to be the latest member of the "Model M-e" pre-Modular (pre-MPOS) series.

"M-e" Modular ANPOS Keyboard (2008)

More information: Model M-e Modular 67-Key POS, MANPOS & MCANPOS Keyboards#MANPOS

eg, P/Ns 00DN181, 93Y1231, 3AA01195500

The Modular ANPOS Keyboard (MANPOS, aka ANPOS II) is the direct successor to the original "Model M-e" based PS/2 ANPOS Keyboard. Being a Modular POS (MPOS) series device, the MSR and key lock are now attachments instead of fixed components and the design now gains a touchpad compared to a PS/2 ANPOS Keyboard or any pointing device compared to an M9. In terms of layout modification, the changes are tame - only 3 programmable keys have moved to make way for the pointing module, thus is likewise available in 116-key (US English) and 117-key (rest of world) layouts. The status indicators panel is also much smaller now. Like its predecessor, it uses IBM buckling rubber sleeves keyswitches. Since 2012, these have been produced and branded by TGCS.

"M-e" Modular CANPOS Keyboard (2008)

More information: Model M-e Modular 67-Key POS, MANPOS & MCANPOS Keyboards#MCANPOS

eg, P/Ns 00DN121, 93Y1223, 3AA01200500

The Modular Compact ANPOS Keyboard (MCANPOS, aka CANPOS II) is the direct successor to the original "Model M-e" based CANPOS Keyboard and is a part of the Modular POS (MPOS) series. Like CANPOS, MCANPOS fits a full-size keyboard and many programmable keys in a chassis that is a similar width to a tenkeyless keyboard. Additionally, all alphanumeric keys are slightly thinner compared to their M9 RANPOS, M-e PS/2 ANPOS and M-e MANPOS counterparts. MCANPOS made many of CANPOS's features modular but it also added the possibility of a key lock and a touchpad that the original CANPOS could never have. No extra keys were added despite some programmable key layout alterations, meaning both CANPOS and MCANPOS have 133 (US English) or 134 (rest of world) keys. Extra status indicators were also added; CANPOS only had three keyboard lock-lights, MCANPOS adds a "Wait", "Offline", "Message Pending" and a user-definable light. Like its predecessor, it uses IBM buckling rubber sleeves keyswitches. Since 2012, these have been produced and branded by TGCS.

"M-e" Modular 67-Key POS Keyboard (2008)

More information: Model M-e Modular 67-Key POS, MANPOS & MCANPOS Keyboards#M67POS

eg, P/Ns 00DN207, 65Y4045, 65Y4045, 3AA01201800

The Modular 67-Key POS Keyboard is the direct successor to the Model M7 and M7-1 50-key POS Keyboards and thus occasionally referred to as the M7-e in fan circles. As its name implies, the M7-e adds 17 keys over its predecessor, however, these new keys are arranged around the same basic layout as the original 50-key M7 to allow for some familiarity for IBM's customers upon upgrading and preserve application-level compatibility. Also included from the M7 design is a dedicated Ctrl key that cannot be reprogrammed and same numeric keypad with a double-width 0 key by default, giving the design 65 total programmable keys out of the box. Being a Modular POS (MPOS) series device, the MSR and key lock are now modular attachments instead of fixed components. Like its predecessor, it uses IBM buckling rubber sleeves keyswitches. Since 2012, these have been produced and branded by TGCS.

"M-e" Modular 67-Key POS LCD Keyboard (2011)

More information: Model M-e Modular 67-Key POS, MANPOS & MCANPOS Keyboards#M67POSLCD

eg, P/Ns 00DN136, 65Y4044, 7431184, 3AA01202800

The Modular 67-Key POS LCD Keyboard is the direct successor to the Model M8 50-key POS LCD Keyboard and is thus occasionally referred to as the M8-e in fan circles. As its name implies, the M8-e adds 17 keys over its predecessor, however, these new keys are arranged around the same basic layout as the original 50-key M8 to allow for some familiarity for IBM's customers upon upgrading and to preserve application-level compatibility. Also included from the M8 design is a dedicated Ctrl key that cannot be reprogrammed and the same numeric keypad with a double-width 0 key by default, giving the design 65 total programmable keys out of the box. Being a Modular POS (MPOS) series device, the MSR and key lock are now modular attachments instead of fixed components. Like its predecessor, it uses IBM buckling rubber sleeves keyswitches. Since 2012, these have been produced and branded by TGCS.

Unicomp New Model M (2020)

More information: Unicomp New Model M

eg, P/Ns UB40U4A, UT40U4A

The New M was the first true new buckling spring Model M variant introduced in 20 years, made with new tooling and thus not prone to the dimples and blemishes Unicomp's older products suffer with. It's essentially the successor to the Unicomp Ultra Classic, taking up a market position of being a bezel-reduced Model M compared to the IBM Enhanced Keyboard/Unicomp Classic. Stylistically, the New M is much closer than its predecessor to typical Model M design features. It is presently only available in black.

Unicomp Mini Model M (2021)

More information: Unicomp Mini Model M

eg, P/Ns UB40E7A, UT40E7A

The Unicomp Mini Model M (or simply "Mini M") is the long-awaited spiritual successor to the IBM Space Saving Keyboard (SSK) and is presently the latest Model M variant introduced. It was announced in December 2019^[120][120]
Unicomp - 2019-12-20 Facebook Post [accessed 2023-02-20]. and finally started shipping in March 2021^[121][121]
Unicomp - 2021-02-24 Facebook Post [accessed 2023-02-20].. Whilst the Mini M is based on the SSK's core design, it sports an upgraded membrane assembly matrix and USB interface capable of larger key combinations around the alphanumeric keys, [blue] lock-light LEDs, a modular and pressure-locking Type-A USB port, and is available (and presently only) in black. The left/right bezel footprint is also slightly diminished compared to the SSK, similar to the Type III/IV 122-key Model M's and matching Unicomp New Model M's side edge-to-key bezels. Like the New Model M, this keyboard is built with Unicomp's latest tooling which is a marked improvement over the quality of the aged tooling other Unicomp keyboards are currently produced with.

Part number list

1232 part numbers have been found in the ASK Keyboard Part Number Database. If you believe a relevant part number is missing, you can help improve this list by requesting a submission for it to be added.

Further reading & resources

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External

Sources

ASK. Admiral Shark's Keyboards original content. License/note: CC BY-NC-SA 4.0.

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