Model M6 & M6-1 ThinkPad Laptop Keyboard Assemblies

Also applies to Lexmark Notebook Keyboard with 16mm Trackball, Lexmark Notebook Keyboard with Integrated Pointing Stick & Lexmark Notebook Keyboard with Integrated Mouse Key

The Models M6 and M6-1 were two IBM buckling rubber sleeve based keyboard assemblies predominately for portable computers, introduced in 1992 and 1993 respectively as part of the IBM Model M keyboard family as the spiritual successors to the Model M3-based keyboard assembly used on the IBM Personal System/2 L40SX laptop. For IBM, M6 and M6-1 became their flagship laptop keyboard designs used on a couple of pre-ThinkPad laptops and many early ThinkPads, typically laptops IBM largely manufactured themselves. They were first produced for IBM by Lexmark, who also used derivative designs for their OEM laptops that were rebranded for various other companies or later self-branded as Lexmark Lexbooks. As a result, the M6 family became a very diverse subfamily within the already large family of Model M keyboards. All M6 family keyboard assemblies, bar two, included an integrated pointing device of some kind; for IBM, their famous TrackPoint pointing stick; for Lexmark, their FSR pointing stick or a 16mm trackball. Industry trends towards increasingly thinner laptops resulted in the M6 family being phased out through the latter half of the 1990s, but their legacy remains; they were a large part of the ThinkPad's success and their reputation of being a 'typist's laptop', and were perhaps amongst the most influential portable computer keyboard designs of all time. The latest observed production year for an M6-1 was 1999^[1][1]
u/themavery - A NOS IBM Model M6-1 ThinkPad 365 Keyboard Assembly [accessed 2023-06-27]..

Contents

Summary

Design

Key-switches

More information: IBM buckling rubber sleeve

The Model M6 family used IBM buckling rubber sleeve (known simply as [IBM] buckling sleeves) key-switches as a hold-over from their Model M3 origins. Thanks to M3 and M6, buckling sleeves were IBM's primary portable computer key-switch technology for the first half of the 1990s and were adopted on the many laptops described in Known variants section. Unlike generic rubber dome key-switches, the rubber component in [IBM] buckling sleeves plays no part in pressing down on the membrane assembly's contacts. Instead (and for IBM buckling sleeves in general), the design offloads this duty to rods on the keycaps or barrel-mounted sliders depending on the specific implementation, either of which descend through the keyboard's key-switch barrels to provide a solid actuation interface. This effectively eliminates the mushy feeling of bottoming out on rubber dome keyboards whilst still keeping the design tactile and relatively quiet. IBM buckling sleeves are very snappy and quite tactile with what's perhaps best described as a medium stiffness feel relative to other key-switch designs.

The Model M6 family exclusively used barrel slider actuation based IBM buckling sleeves (aka, "Model M6/M6-1 type"). This type used a barrel slider for actuation and had a crosspoint keycap mount that vastly simplified keycap removals and replacement over the rod-actuated Model M3's buckling sleeves. More than any other IBM Model M with buckling sleeves, M6s could sport a variety of different sleeve gauges to suit very specific key sizes. Generally, primary (alphanumeric, modifier, etc.) keys used standard or alt-standard gauge sleeves and medium, alt-medium and small gauges were used for various secondary (function, navigation, etc.) keys. Generally, the sleeve colour would reflect the host keyboard's colour (white keyboards get grey sleeves, black keyboards get black sleeves) but there are outliers - for example, all small gauge buckling sleeves are clear-transparent regardless of host keyboard colour. Specific combinations are noted in the aforementioned Known variants section. A version of the M6's buckling sleeve implementation, early POS type IBM buckling sleeves, would be adopted for early IBM/Toshiba Retail POS (Model M7, M7-1, M8, M9 and M11) keyboards.

M6/M6-1 type IBM buckling sleeves at standard key-size positions are uniquely capable of supporting their sleeves upside-down thanks to recesses in M6/M6-1 keyboards' frame. It's unclear why these are present and if the switches were ever practically deployed like this. One can flip the sleeves themselves, though it can lead to a mushy key-feel.

Assembly

Model M6 family keyboard assemblies are comprised of four distinct layers; the keyboard frame, the membrane blanket, the membrane assembly and the base plate.

Unique to some keyboards

Several Model M6 family keyboard assemblies additionally had an outer frame acting as the top layer since the keyboard itself serves as the top cover to the laptop's base. Known M6s and M6-1s like this include:

Keycaps

The Model M6 family keyboards' keycaps were based on the sculpture of their Model M3 (and M4/M4-1) predecessors, though some changes have been made. Whilst those keycaps were known to be PBT, Model M6 family keyboards [that are overall black] appear to be made of ABS instead - an already damaged keycap was tested against acetone and was found to be dissolvable, which is expected of ABS but not PBT. However, the limited examples of pearl white or grey M6s and M6-1s don't seem to 'yellow', so those were likely made of PBT instead. Legend printing methods seemed to have varied, with some having 'textured-looking' legends (likely silk-screened) and others with extended outlines (likely pad-printed). Some IBM-branded white or grey M6s and M6-1s also appeared to use dye-sublimation as well (though Lexmark-branded keyboard white or grey keycaps didn't).

In line with the change in specific IBM buckling sleeves implementation, M6s and M6-1s also differ from M3 in keycap mount. Whilst M3s (and M4s and M4-1s) used two clips on either side of the keycap for retaining and a rod plunger for actuation, M6s have a barrel-fixed slider that supports a crosspoint mount similar to what Cherry uses for its MX family of key-switches but smaller and the plug and socket direction reversed (keycap is plug, switch is socket). This allows for easy keycap removal for cleaning and replacements.

Integrated pointing device

Almost all Model M6 family keyboards have an integrated pointing device of some sort. Due to M6s being used during the early stages of laptops sporting an integrated mouse replacement of any kind, several technologies have been spotted including 16mm trackballs, pointing sticks and a mouse-key.

16mm trackball

The Lexmark AR10 OEM series exclusively uses a 16mm trackball located at the bottom-right of the keyboard. This technology is similar to that found on Model M5-1 16mm Trackball Keyboard. When the AR10 was first seen in early 1992, trackballs would have been the obvious mouse device of choice for laptop manufacturers before the release of pointing sticks (like TrackPoint II in late 1992) and trackpads/touchpads.

Note that whilst the IBM PS/2 CL57SX also features a trackball module alongside a Model M6, it is not a part of the keyboard assembly and is housed separately in the laptop (hence not considered an integrated pointing device relative to the keyboard).

TrackPoint strain gauge pointing stick

More information: IBM/Lenovo TrackPoint pointing stick

Most IBM-host Model M6 family keyboard assemblies make use of IBM's famous TrackPoint pointing stick in either its original* revision II or improved revision III. TrackPoint uses strain gauges to register user input and is an "isometric" (non-moving) stick by design. Lenovo - who bought IBM Personal Computing Division in 2005^[5][5]
Lenovo - Lenovo Completes Acquisition of IBM’s Personal Computing Division [accessed 2021-08-21]. - still uses TrackPoints (revision IV) on most of its ThinkPad laptops. The primary difference between TrackPoint II and III is that three includes a negative inertia transfer function in its firmware that greatly improves its performance. Whilst suitable for period laptop resolutions, by contrast, TrackPoint II can appear sluggish at modern resolutions.

M6s and M6-1s that sport TrackPoints don't have onboard controllers for their sticks unlike most TrackPoint IV keyboards from the late '90s onwards, meaning the firmware difference between II and III is laptop-side only. An M6 family keyboard assembly's use of either TrackPoint II or III can only be confirmed by knowing the host ThinkPad's specifications. The stick assembly was revised once:

Lexmark-Unicomp force-sensing resistor pointing stick

More information: Lexmark-Unicomp FSR pointing stick

The Lexmark-Unicomp pointing stick (provisional name) is an alternative pointing stick to TrackPoint used on some non-IBM branded M6s and M6-1s such as AST Ascentia 900N series (later models), Lexmark GS20 series and Winbook XP series keyboard assemblies. Both TrackPoint II and the Lexmark-Unicomp stick are derived from the same patent. Instead of using strain gauges as sensors like TrackPoint II through IV, this stick uses force-sensing resistors (FSRs) as sensors instead. Unlike its IBM counterpart which never physically moves, the FSR stick moves moves slightly and acts like a small joystick. Unicomp still uses a longer version of this pointing stick on their EnduraPro keyboards.

Mouse Key pointing device

The Lexmark Lexbooks MB10, MB15 and SE10 used a unique pointing device called a "Mouse Key" (branded, stylised as "mouse-key" generically speaking). The Lexmark Mouse Key was located in the bottom-rightmost corner of their host keyboards. They acted like joysticks (so the underlying technology may be based on Lexmark's FSR pointing stick) but with a keycap-style cap on top. The Mouse Key cap resembled a 1-unit sized keycap but the device consumed 1.25 units of key-space to give it some clearance.

OEMs & rear labels

IBM U.S.

Some early Model M6 family keyboard assemblies destined for IBM-branded laptops such as the IBM PS/2 CL57SX and PS/note 182 series seem to have been made by IBM themselves in the United States. Whilst Lexmark had been founded by early 1992, IBM was still known to make keyboards itself in the U.S. during this time as Lexmark only inherited IBM's facilities in Boulder, Colorado and Lexington, Kentucky^[7][7]
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].. Such keyboards use rear label styles inherited from their Model M3 (IBM PS/2 L40SX) successor though with an added "FRU No." field.

Lexmark U.S.

Between 1993 and 1995, Lexmark in the United States was primarily responsible for Model M6 family keyboard production. Lexmark U.S. rear labels for keyboard assemblies destined for IBM-branded laptops almost always showed their "M6" or "M6-1" designation with only a couple of exceptions. The sticker style changed over those years, though it always resembled the rear labels found on typical desktop Model M keyboards of the period. Early and late rear labels were usually rectangular, but during the time between them, various square-shaped labels were also used. Variants of the mid and late rear labels exist.

For the keyboard assemblies Lexmark U.S. produced for their own laptop designs (for example, AR-10 and GS-20 series) for their Lexbook brand or third-party rebrands, Lexmark used a very simple rear label that showed only an assembly number and manufacture date.

For Model M6 family keyboard assemblies Lexmark U.S. produced and supplied for third-party brands' original laptop designs, Lexmark used rear labels based on period IBM-style rectangular designs but with generally less detail and no "Model M" designation. For Winbook XP/XP5 series laptop keyboard assemblies, their real labels had only a few fields written on them. For AST Ascentia 9X0N series keyboard assemblies, their rear labels had more fields including two part numbers (AST's and Lexmark's) and a revision field. The Lexmark-AST rear label has two variants; one with a barcode on it and another without (the barcode was instead present on a second sticker).

Lexmark U.K.

On occasion, Lexmark sourced Model M6 family keyboard assemblies from the UK (at the IBM Greenock, Scotland plant). Typically, UK Model M production of any kind was intended for the production or assembly of IBM systems destined for sale in Europe, Middle East and Africa (EMEA). But US English Model M6 family keyboard assemblies have also been made in the UK^[10][10]
ASK Keyboard Archive - P/N 84G6445 (1995, Lexmark) [accessed 2023-07-07]. License/note: photos saved from volatile eBay listing, used under fair dealing., so it's also possible UK production was also used to enhance production capacity for laptops destined anywhere in the world. Lexmark U.K. Model M6 family keyboard assemblies don't have any noticeable physical or operational differences from their US-made counterparts, though their rear labels were different and never displayed a "Model M6" designation.

Key Tronic

After Lexmark exited the keyboard market in April 1996, Key Tronic immediately assumed most non-retail market buckling sleeve Model M keyboard production, including for the Model M6 family. Other than variations on the keys' legend printing, Key Tronic made M6-1s generally don't have noticeable differences from their preceding Lexmark counterparts. Key Tronic produced M6-1s in both the US ("KTC1") and Mexico ("KTC2" and "KTC3"). The original Key Tronic rear label style for IBM keyboard assemblies was just a modification of one Lexmark used with a slightly different font, but eventually, Key Tronic introduced their own style that included "IBM Model M6-1" placed at the bottom-right under the ID number barcode and added as Key Tronic specific "Model" field with a nomenclature of U0405xxx. The later style could be found with small or large rounded corners.

Key Tronic made M6-1s for non-IBM laptops had rear labels like later IBM-destined keyboard assemblies, but lacked a "Model M" designation and the barcode is the part number instead of the ID number.

M6 versus M6-1

The defining difference between keyboard assemblies designated "M6" and "M6-1" is somewhat open for debate. This is despite the fact other numbered Model M variants that additionally have dashed subvariant numbers have clear, observable differences:

Additionally, whilst some keyboard assemblies were clearly designated "M6" or "M6-1", some lack any designation despite clearly having M6 or M6-1 properties. This has blurred the line between what makes an "M6" an "M6" or an "M6-1" an "M6-1". There are three theories as to what the distinction may be that mostly rely on IBM's use of the "M6" and "M6-1" designations alone and then work or don't work when scaled to include non-IBM keyboards. Those theories are:

"Outer frame theory"

One suggested distinction appears to be the use of an outer frame. IBM keyboards designated "M6" sit underneath a top case piece of some sort and are screwed into place, whereas those designated "M6-1" have their own plastic frame that is not screw-attached to the keyboard assembly. This outer frame is present since most IBM ThinkPads that use M6-1s use the keyboard as a functional lid to the base of the laptop. As such, an M6-1 has two hinges and facilitates two slide-locking mechanisms from the laptop itself.

The problem with this theory is that examples of non-IBM keyboard assemblies that are still designated "Model M6-1" without individual outer frames - despite being rare - are known. For example, Lexmark OEM Tadpole SPARCbook 3/3000 series keyboard assemblies have been seen with a [legible but barely] "M6-1" designation but are screw mounted to a laptop's top case piece just like any designated "M6" keyboard assembly^[13][13]
Ray Arachelian - Hacking the SPARCbook V1.1-2000.05.10 [accessed 2023-05-27].. Given such designations can extend outside IBM, this would also mean that a technical M6-1 would predate most M6s as the Lexmark AR10's keyboard assembly has an outer frame yet predated IBM's designated M6-1s by over a year. As such, this theory doesn't scale with all M6 family keyboards.

"Barrel slider shape theory"

Another suggested distinction is the shape of the IBM buckling sleeves' barrel sliders' mount used for grabbing keycap stems. IBM keyboards designated "M6" appear to have a minimalistic mount that's very hollow and 'skeletal', whereas those designated "M6-1" appear to have a mount more robust and solid. Whilst this difference doesn't break keycap compatibility, it is observable.

Some very early "M6-1" designated keyboard assemblies (for the IBM ThinkPad 750 series) have been spotted with 'skeletal-style' sliders. Whilst like the previous theory, this is an [relatively] uncommon exception, it's a problem with this theory nonetheless.

"Barrel slider colour theory"

Yet another possible distinction appears to be the colour of the barrel slider present for attaching keycaps to the keyboard and being the plunger that actuates the membrane assembly within the keyboard assembly. IBM keyboards designated "M6" appear to have brown sliders, whereas those designated "M6-1" appear to have black sliders. This theory doesn't conflict with the M6-1 designated Lexmark OEM Tadpole SPARCbook 3/3000 series keyboard assembly that is evidence against the outer frame theory since the very same keyboard has black sliders visible in another photo^[13][13]
Ray Arachelian - Hacking the SPARCbook V1.1-2000.05.10 [accessed 2023-05-27].. This theory also avoids the conflict from sorting by barrel slider shape, as early IBM ThinkPad 750 series keyboards conform to this.

Decision

Admiral Shark's Keyboards currently practises the "barrel slider colour theory" since there is no [obvious] contrary evidence at this time. This means non-designated keyboard assemblies that are clearly related to designated M6s and M6-1s are given a provisional "M6" or "M6-1" designation based on the observed barrel slider colour. This means that "M6" and "M6-1" doesn't really matter to the end user, and instead, a Type system is described below to provide better categorising of known M6 family keyboard assemblies. Should a better understanding or contrary evidence be found, these designations will be subject to review to best fit all known facts.

Types

All known Model M6 and M6-1 keyboards belong to one of six layout and form-factor lineages referred to as "types". These types are not official IBM/Lexmark/Unicomp (etc.) nomenclature but instead invented to produce easy identification. Type numbers were assigned chronologically based on the first example of a given layout/form-factor combination.

Type I Model M6

The Type I Model M6 was the original form of the Model M6 keyboard assembly solely found on the IBM PS/2 CL57SX and its Japanese PS/55 counterpart, and thus first appeared in February 1992 when those laptops were announced^[2][2]
Ardent Tool - IBM PS/2 Model CL57 SX System 8554-A45 and Features Announcement Letter (#ZG92-0165) [accessed 2023-07-13].. This type of keyboard resembles that of an IBM PS/2 L40SX keyboard assembly (Model M3-based) or even an IBM Space Saver Keyboard (Model M4) but with black casing and keys. Despite the obvious similarity and use of standard gauge IBM buckling sleeves, Type I M6s have the barrel sliders M6s are known for. Being limited to the CL57SX, this type is the least common. Whilst the CL57SX had a trackball pointing device, its assembly is separate from the keyboard's, thus Type I M6s are considered to not have any pointing device.

Type II Model M6

The Type II Model M6 was the earliest form of Model M6 keyboard assembly with an integrated pointing device, which debuted with Lexmark's AR10 OEM series laptop by March 1992^[17][17]
PC Mag - 31 Mar 1992 [accessed 2023-05-11]. License/note: accessed via Google Books.. This type of keyboard retains most of the Model M3's and Type I M6's key unit sizes including their characteristic smaller square keys around the main alphanumeric and modifier keys section. However, those smaller square keys are arranged differently to reduce the overall width of the keyboard and effectively popularised the 7-row keyboard layout 'classic' IBM and Lenovo ThinkPads are known for (note that the ThinkPad community doesn't consider the 3 bottom arrow keys to be a separate row, hence 7-row instead of 8) alongside other non-M6 IBM PS/2 note laptops. IBM adopted keyboard assemblies that were visually based on the Lexmark OEM design both with and without a pointing device for itself on the IBM PS/note 182 series (no pointing device), IBM ThinkPad 350 series and IBM PS/note 425 series (both equipped with TrackPoint II pointing sticks). Lexmark used Type II M6s for the aforementioned AR10 series and GS20 series laptops with an integrated 16mm trackball and FSR pointing stick respectively. Due to the positioning of the AR10 trackball, the arrow keys on Lexmark AR10 and GS20 keyboards are shifted leftward to provide space for it. Type II M6s used either standard (usually for white keyboards) or alt-standard (for some black keyboards) gauge IBM buckling sleeves.

Type III Model M6/M6-1

The Type III Model M6 and M6-1 (along with Type V) are the most recognisable Model M6 family keyboards assemblies. Type III was introduced with the IBM ThinkPad 700 series and IBM PS/55 note C52 in October 1992^[18][18]
Ardent Tool - IBM ThinkPad 700 and 700C PS/2 Systems Brief Description of Announcement, Charges, and Availability (#192-256) [accessed 2023-05-10].. Type III was the first M6 subtype to always have an integrated pointing device. Likely to reduce the overall depth over the Type I and Type II, the function, navigation and arrow keys on Type III had reduced depth to compact their rows. With only minor alterations, IBM and later Lenovo retained this style as the main ThinkPad keyboard style until 2012 when Lenovo introduced their AccuType keyboard style to the xx30 generation ThinkPads. Type III M6s consisted of the aforementioned IBM ThinkPad 700 and PS/55 note C52 series and the ThinkPad 720 series. The Type III form was later revived for various Tadpole laptops and the related IBM RS/6000 Notebook N40, but this time as a Model M6-1 design. Type III was directly succeeded by Type V for consumer IBM ThinkPads, which whilst similar in layout, differed in how they attached to their host; Type III was an embedded keyboard design (the laptop base's top case piece surrounds the keyboard), and Type V was hinged and thus acted as a cover/lid to the base of the laptop. Type III M6s most often used alt-standard and alt-medium gauge IBM buckling sleeves for main (alphanumeric, modifier, etc.) and secondary (function, navigation, etc.) keys respectively, though Type III M6-1s used standard and medium gauge instead.

Type IV Model M6-1

The Type IV Model M6-1 was effectively a scaled-down Type III design originally intended for a select few subnotebooks as a 6-row keyboard. The key unit sizes are slightly smaller compared to all other M6s and M6-1s and typically used medium gauge IBM buckling sleeves for most keys and small gauge for the top row of [usually] escape, function and navigation half-depth keys. The Type IV design debuted in June 1993 with the IBM ThinkPad 500 series^[20][20]
IBM - IBM ThinkPad 500 Brief Description of Announcement, Charges, and Availability (#193-167) [accessed 2023-05-12]., which had a TrackPoint II pointing stick, a full row of keys at the top, a cluster of half-depth keys in the bottom-right corner and no mouse keys (which were a separate subassembly in the laptop). The slightly later IBM ThinkPad 510Cs also employed this keyboard with extremely minor revision. Lexmark's MB10 and MB15 adopted a similar keyboard design with two fewer keys in the top row, full-size arrow keys and a mouse-key pointing device instead of IBM's half-depth key cluster in the bottom-right. Two mouse button keys were also inserted in between the Ctrl and Alt keys. The Lexmark SE10 used a similar keyboard to MB1X but the top row was 'restored' to the ThinkPad 500/510's style. Finally, a very similar keyboard assembly was utilised for the Apple Newton MessagePage Keyboard (X0044), which lacked any integrated pointing device or half-depth keys and indeed the top key row at large. The laptop version of the keyboard is referred to as "Type IV(A)" and the X0044 as "Type IV(B)".

Type V Model M6-1

The Type V was an evolution of the Type III M6/M6-1 that instead of being mounted within its host laptop, it became the lid of the base and was hinged to allow them to lift like a car's bonnet (hood in U.S. English) to access the host's main components. Two slide locks are present on the laptop to secure the keyboard once when it's lowered. The Type V was introduced with the IBM ThinkPad 750 series in September 1993^[21][21]
IBM - IBM ThinkPad 750, 750Cs, 750C and 750P Systems and Related Optional Features Brief Description of Announcement, Charges, and Availability (#193-269) [accessed 2023-06-25].. In terms of layout, the only difference is the inclusion of an Fn key that the IBM ThinkPad 700 and 720 series' Type IIIs lacked. Two versions of Type V exist - the original ("Type V(A)", if you will) keyboard assembly that had a TrackPoint II pointing stick and two thin and entirely red mouse buttons and the later ("Type V(B)") keyboard assembly that had a TrackPoint III pointing stick and two larger mouse buttons that can be mechanically locked by sliding them forward. All Type V M6-1s use standard and medium gauge IBM buckling sleeves for main (alphanumeric, modifier, etc.) and secondary (function, navigation, etc.) keys respectively. The original design was used for the IBM ThinkPad 355, 360, 370C, 750 and early 755C series, and the second design was used for the 365 and late 755C series and Power Series 850 and RS/6000 Notebook 860. No non-IBM branded Type Vs are known and this would be the last IBM Model M family keyboard design for ThinkPads.

Type VI Model M6-1

The Type VI Model M6-1 was the final unique M6 family design introduced. As a space-saving 6-row design, it resembles an enlarged Type IV M6-1, but it returned to using standard base key unit sizes and standard gauge IBM buckling sleeves for most keys except the top row (which retained small gauge sleeves). It first appeared as the keyboard assembly for Winbook XP series laptops seen as early as May 1994^[22][22]
InfoWorld - 31 May 1994 [accessed 2023-05-14]. License/note: accessed via Google Books.. A reskinned version of Type VI was also used for the AST Ascentia 900N series. Type VI has the distinction of being the only M6 family keyboard design that has no Lexmark self-brand or IBM-branded counterparts, thus it's likely this was a Lexmark OEM only keyboard design. Most Type VIs used an FSR pointing stick, though AST versions of the keyboard have been spotted with TrackPoint II pointing sticks. In terms of layout, Type VIs are easily identifiable for their 1-unit sized right shift and num-lock keys in the lower right and page down key placed right of the backspace key. Also unique is that instead of having a reduced left shift key to make way for an extra key, locales that would traditionally have an ISO physical layout keyboard instead get an extra key placed right to the spacebar^[23][23]
ASK Keyboard Archive - P/N 232011-001 (1995, Lexmark) [accessed 2023-05-22]. License/note: photos saved from volatile eBay listing.. The major difference between the Winbook and AST physical layouts is that the Winbook's "1/!" key has a plastic protrusion to extend the key to the edge whereas the AST keyboard is fitted into a plastic frame that covers this excess area.

Known variants

IBM PS/2 CL57SX (1992)

Summary: Type I Model M6, brown skeletal barrel slider, no integrated pointing device, made by IBM U.S. & Lexmark

The IBM 8554 PS/2 CL57SX was a microchannel architecture (MCA) laptop with a 20MHz Intel 386SX CPU announced on 25th February 1992 in EMEA^[2][2]
Ardent Tool - IBM PS/2 Model CL57 SX System 8554-A45 and Features Announcement Letter (#ZG92-0165) [accessed 2023-07-13]. and 24th March 1992 in the USA and made available on 17th April 1992^[25][25]
IBM - IBM PS/2 Model CL57 SX System and Features Brief Description of Announcement, Charges, and Availability (#192-073) [accessed 2023-07-13].. It was IBM's first colour screen laptop^[26][26]
Wikipedia - IBM PS/2 Model CL57 SX [accessed 2023-05-15].. Effective 15th December 1992, the IBM 8554 was withdrawn from marketing and IBM designated the ThinkPad 700C as its successor^[27][27]
IBM - Withdrawal: Selected IBM PS/2 Portable System Units (#192-301) [accessed 2023-07-13]..

The 84 (ANSI) or 85-key (ISO) 8554 keyboard assembly was the earliest Model M6 keyboard assembly observed, originally made by IBM U.S. then later Lexmark for IBM^[28][28]
Ardent Tool - PS/2 Model CL57 SX [accessed 2023-05-15].. The basic layout and style were directly borrowed from the IBM PS/2 L40SX's Model M3-based keyboard but the overall keyboard was now coloured 'raven black' (IBM's trade name for a black product colour) instead. Whilst the CL57SX notably has a trackball positioned on the right side of the laptop and just above the keyboard, the trackball assembly is separate from the keyboard and not attached in any way^[29][29]
Hrushka via iFixit - IBM PS2 CL57 SX Disassembly#Step 2 [accessed 2023-05-16].. 8554 keyboards have 13978xx part number and 13979xx FRU number nomenclatures. This keyboard also establishes some styling cues and features future PS/note and ThinkPad laptops would have such as golden modifier, lock and utility key legends. The 8554 keyboard can have an overlay numeric keypad, and when present, its legends are coloured dull blue. However, some examples such as the French AZERTY version lack an overlay numeric keypad altogether^[29][29]
Hrushka via iFixit - IBM PS2 CL57 SX Disassembly#Step 2 [accessed 2023-05-16]..

IBM PS/55note N27sx (1992)

Summary: Type I Model M6, [presumably] brown skeletal barrel slider, no integrated pointing device, [presumably] made by IBM U.S. & Lexmark

The IBM 5527 PS/55note N27sx was the Japanese-exclusive release of the IBM 8554 PS/2 CL57SX. It was likewise a microchannel architecture (MCA) laptop with a 20MHz Intel 386SX CPU; whilst CL57SX was the first colour PS/2 laptop, the N27sx was the first colour PS/55 laptop. N27sx was released in February 1992 and included the variants 5527-U08 (without OS/2), 5527-UZ8 and 5527-UZB (both with OS/2 J2.0)^[30][30]
anonidadoko.sakura.ne.jp - PS/55note [accessed 2023-07-09]..

The 5527 keyboard assembly was clearly related to the CL57SX's Type I M6-based keyboard assembly though its physical layout differed to suit the host market. Like the CL57SX's keyboard assembly, it was an evolution of the IBM PS/2 L40SX's Model M3-based keyboard but altered to specifications expected of M6 family keyboards. Though the 5527 keyboard assembly differs from the CL57SX's by layout - the keyboard assembly was modified to accommodate an 89-key Japanese JIS style layout with fewer key unit size compromises for the main alphanumeric, modifier and utility keys but at the expense of 6 navigation keys that have been shrunk width-wise. Presumably, most keys use standard gauge IBM buckling sleeves like its CL57SX counterpart, but it's unclear what sleeve gauge is used for the narrower navigation keys due to lack of photo evidence (it's possible this was the introduction of the medium gauge sleeve to suit them). The 5527 keyboard assembly retains golden modifier, lock and utility key legends and blue overlay numeric keypad legends (though more vibrant than its Western counterpart). Again presumably, the N27sx's trackball assembly is separate from the keyboard, thus the keyboard is considered to not have an integrated pointing device.

Lexmark AR10 OEM series (1992)

Summary: Type II Model M6, brown skeletal barrel slider, 16mm trackball, made by Lexmark

The Lexmark AR10 was a series of laptops produced by Lexmark for their own Lexbook branding and to serve as a template for laptops for other companies to brand. The earliest AR10-based laptop known, the CompuAdd Express 325NXL, was seen as early as 31st March 1992^[17][17]
PC Mag - 31 Mar 1992 [accessed 2023-05-11]. License/note: accessed via Google Books.. Other known AR10 based laptops include the ComputAdd Express 325FTX, CompuAdd Express 425CXL (seen December 1992)^[32][32]
PC Mag - 8 Dec 1992 [accessed 2023-05-11]. License/note: accessed via Google Books., CompuAdd Express 425FTX, Cube ProBook 425NTX (May 1993)^[33][33]
InfoWorld - 24 May 1993 [accessed 2023-05-11]. License/note: accessed via Google Books., Hyundai Courier Spectra (March 1993)^[34][34]
PC Mag - 30 Mar 1993 [accessed 2023-05-11]. License/note: accessed via Google Books. and their own Lexmark Lexbook AR10 (March 1994)^[35][35]
Computer Business Review (CBR) - Lexmark launches Lexbook end-user portable line [accessed 2023-05-11]..

The keyboard itself was branded the Lexmark Notebook Keyboard with 16mm Trackball and was used extensively in advertising Lexmark's keyboard portfolio. The AR10 keyboard assembly (along with the GS20's) has all the technical traits of a Model M6 but essentially represents a stepping stone between M6s such as the IBM PS/2 CL57SX's that looked basically the same as the earlier Model M3 found on the IBM PS/2 L40SX from the outside and familiar classic IBM ThinkPad 'true' M6s and M6-1s. The AR10 keyboard has a ThinkPad-like 7-row layout that ThinkPads would later be well known for but retains the smaller square keys around the main alphanumeric and modifier keys section that was characteristic of the M3 (and by extension, M4/M4-1 desktop keyboards). In that regard, it seems the AR10/GS20 keyboard design also served as the basis for various IBM-branded M6s such as the PS/note 182's, ThinkPad 350's and PS/note 425's. The arrow keys are shifted to the left to make way for the 16mm trackball assembly. The mouse buttons for it were placed in between the left Ctrl and Alt keys labelled "M1" and "M2" and used mouse button type IBM buckling sleeves. The sole known part number for an AR10 keyboard assembly is 1399300 for a US-English layout keyboard. Its keycaps were white and grey, differing from IBM's classic pearl and pebble keycaps as Lexmark used chromatically cooler colours. An overlay numeric keypad is present and its legends are coloured in a vibrant blue.

IBM ThinkPad 700 (1992) & 720 series (1993)

Summary: Type III Model M6, brown skeletal barrel slider, TrackPoint II pointing stick, made by Lexmark

The IBM 9552 ThinkPad 700 (monochrome display) and 700C (colour display) were two microchannel architecture (MCA) laptops with [from-factory] IBM 486SLC CPUs announced by 5th October 1992 and released on 30th October and 16th October 1992 in the United States respectively^[18][18]
Ardent Tool - IBM ThinkPad 700 and 700C PS/2 Systems Brief Description of Announcement, Charges, and Availability (#192-256) [accessed 2023-05-10].. In EMEA, they were released sometime in October (DOS models) or November (OS/2 models)^[37][37]
IBM - The IBM ThinkPad 700 PS/2 (9552-A95), (9552-A97) and (9552-597) and IBM ThinkPad 700C PS/2 (9552-B97) and (9552-697) Announcement Letter (#ZG92-0342) [accessed 2023-05-10].. In the eyes of many fans, the ThinkPad 700 series constitutes the first 'true' ThinkPads (ie, a bento box style laptop with a red nub pointing device). The 700 series was followed by the IBM 9552 ThinkPad 720 series, which was visually identical and likewise available in a non-"C" monochrome and "C" colour model, but used IBM 486SLC2 CPUs from the factory (which was previously only an upgrade option for the 700 series). 720 and 720C were both released on 4th May 1993 in the United States^[38][38]
Ardent Tool - IBM ThinkPad 720 and 720C PS/2 Systems Brief Description of Announcement, Charges, and Availability (#193-116) [accessed 2023-05-10]. and were the last IBM laptops to use MCA. The 700 and 720 series were withdrawn effective 8th October 1993^[39][39]
IBM - Withdrawal: Selected IBM PS/2 Mobile Systems (300, 700/700C) and Features (#193-268) [accessed 2023-07-13]. and 22nd March 1994^[40][40]
IBM - Withdrawal: Selected IBM Mobile Systems (720/720C and one model of 710T with PenPoint 1.01) and Features (#194-047) [accessed 2023-07-13]. respectively.

The 9552 family introduced the Type III Model M6, which further evolved the 7-row keyboard layout seen on the Lexmark AR10's Type II Model M6 by introducing many reduced depth function and navigation keys as seen on the otherwise [technologically] unrelated keyboard assemblies used on IBM PS/2 note N51 series notebooks from March 1992^[41][41]
ThinkPad-Wiki - N51 [accessed 2023-05-10].. The 9552 keyboard assembly was also the first of any keyboard to introduce the TrackPoint II pointing stick. The combination of the 7-row layout and TrackPoint was the beginning of what fans consider the 'classic' ThinkPad keyboard lineage that was used by IBM and Lenovo with relatively minor revisions until 2011. Both the 700 and 720 share the same pool of keyboard assemblies in the 44G379x (English speaking) and 48G92xx (rest of world) part/FRU number nomenclatures. The 9552 keyboard assembly had various golden modifier, lock and utility key legends and an overlay numeric keypad with dull blue legends. These early ThinkPad M6 keyboards weren't hinged modules like their Type V Model M6-1 successors, instead, they screw-mounted onto a keyboard frame stiffener that wrapped underneath the host laptop's main battery to provide rigidity. For Germany, a grey version of the IBM 9552 was made in an overall grey case with a matching keyboard with classic pearl and pebble keycaps (FRU 48G9236).

IBM PS/55 note C52 (1992)

Summary: Type III Model M6, brown skeletal barrel slider, TrackPoint II pointing stick, made by Lexmark

The IBM 9552 PS/55 note C52 was the Japanese-exclusive release of the IBM ThinkPad 700C likewise available from October 1992^[42][42]
PC Watch - ThinkPad 10th Anniversary Special 10 [accessed 2023-05-10].. It's assumed IBM Japan used the existing "PS/55 note" branding for familiarity. Being based on the 700C, the C52 had an IBM 486SLC CPU and colour display.

Due to its 700C origins, the C52 likewise used a Type III Model M6 keyboard assembly (P/N 44G3620, FRU 44G3796) based on the IBM ThinkPad 700 and 720 series' but with some modifications to suit the Japanese layout. Besides the obvious use of a JIS-like overall physical layout, the Alt keys were shortened from 1.5-unit to 1.25-unit keys, the arrow keys were moved leftward so that the up-arrow key could be placed in between the right Alt and Ctrl keys, and the overlay numeric keypad legends were a deeper blue compared to the 700/720 design. The C52 keyboard assembly was also screw-mounted onto a keyboard frame stiffener that wrapped underneath the host laptop's main battery to provide rigidity.

IBM PS/note 182 series (1992)

Summary: Type II Model M6, brown skeletal barrel slider, no integrated pointing device, made by IBM U.S. & Lexmark

The IBM 2141 PS/note 182 series was an entry-level IBM laptop announced on 6th October 1992^[43][43]
IBM - IBM PS/note model 182 Announcement Letter (#ZG92-0266) [accessed 2023-05-12]. as a cheaper counterpart to the ThinkPad 700 series. At the time of introduction, IBM stated it was their lightest mobile system^[44][44]
IBM - IBM Personal Systems Fall 1992 Announcement Overview (#ZA92-0318) [accessed 2023-05-11]. and was considered to be a member of the IBM PS/1 family^[45][45]
IBM - IBM PS/Note - 2141 - Technical Specifications (#GJAN-433LNT) [accessed 2023-05-11]. License/note: document archived by kev009. (a low-end supplement to the PS/2 line). The 2141 Model 182 would be joined by the 2141-E82, 2141-S82, 2141-M82, 2141-N82 and 2141-W82. Most variants have a 386SL CPU, but the 2141-N82 was known to have a 386SX^[46][46]
Wikipedia - IBM PS/2 Note and PS/note [accessed 2023-05-10]..

The 2141 keyboard assembly was a Type II style M6 design visually based on the Lexmark AR10 and GS20 design but with slightly wider leftmost column keys. Like those Lexmark laptops, the 2141 keyboard assembly resembled a Model M3 L40SX or the IBM PS/2 CL57SX's Type I Model M6 keyboard assembly but sported a ThinkPad-like 7-row layout. Whilst the laptops themselves were a grey colour, the keyboard assembly was black. They had 33G449x, 33G60xx and 33G96xx part and FRU number nomenclatures. The keyboard assembly would sit under the top case piece called a "keyboard cover" (FRU 33G4178). The 2141 keyboard assembly had various gold key legends like other IBM portables that came before but its overlay numeric keypad legends had a deep blue colour unlike most contemporary mainstream ThinkPads but like Japanese PS/55note laptops.

IBM ThinkPad 350 & PS/note 425 series (1993)

Summary: Type II Model M6, brown skeletal barrel slider, TrackPoint II pointing stick, made by Lexmark

The 2618 ThinkPad 350 series were 25MHz Intel 486SL notebooks announced on 15th June 1993 that included the 350 (monochrome) and 350C (colour) models^[48][48]
IBM - IBM ThinkPad 350 and 350C Brief Description of Announcement, Charges, and Availability (#193-166) [accessed 2023-05-15].. The IBM 2618 PS/note 425 series was an alternative badge version of the 350 that likewise had a C and non-C model. Both the ThinkPad 350 and PS/note 425 were withdrawn from marketing effective 20th January 1995^[49][49]
IBM - Withdrawal From Marketing: Selected IBM ThinkPad Systems and Options (#A95-5) [accessed 2023-05-15]. and withdrawn from maintenance effective 31st March 1997^[50][50]
IBM - Notice - Withdrawal of Maintenance Agreement Service - Selected Machines (#A96-712) [accessed 2023-05-15]..

The IBM 2618's Model M6 keyboard assembly was the final Type II design and was essentially the same as the IBM PS/note 182 series' Model M6 (the general keyboard layout and base plate hook positions match) but with an added TrackPoint II pointing stick. The 350 and PS/note 425 both share keyboard part and FRU numbers, which had a nomenclature of 59G75xx and 60Gxxxx respectively. Like the PS/note 182 keyboard assembly, the 2618 keyboard assembly had various gold key legends and its overlay numeric keypad legends had a deep blue colour.

IBM ThinkPad 500 series (1993)

Summary: Type IV Model M6-1, black skeletal barrel slider, TrackPoint II pointing stick, made by Lexmark

The IBM 2603 ThinkPad 500 series were monochrome subnotebooks announced on 15th June 1993. They were small IBM 486SLC2 50/25MHz powered laptops available as a Model 081 with an 85MB hard drive and a Model 171 with a 170MB hard drive released June and August 1993 respectively^[20][20]
IBM - IBM ThinkPad 500 Brief Description of Announcement, Charges, and Availability (#193-167) [accessed 2023-05-12].. Both models of IBM 2603 were withdrawn from marketing effective 13th January 1995^[51][51]
IBM - Withdrawal: IBM ThinkPad 500 Systems and Selected Mobile Features (#194-427) [accessed 2023-05-12]..

The 2603 keyboard assembly was both the first Type IV design and the earliest known Model M6-1 keyboard assembly. Compared to all other types, Type IV used slightly smaller keycaps supported by medium gauge IBM buckling sleeves for all keys except the top function row to reduce overall keyboard footprint. The top function row instead used half-depth (compared to the 'new' already smaller keycaps) keycaps with small gauge sleeves underneath, and the IBM 2603 is currently the earliest known confirmed host of that gauge. Being a Model M6-1 instead of M6, the IBM buckling sleeves' barrel sliders are black instead of brown. IBM managed to fit almost all the keys of a regular contemporary 7-row ThinkPad keyboard (81 versus the typical 85 ANSI/86 ISO keys) into this footprint, which resulted in some compromises such as the cluster of half-depth keys in the bottom-right corner. The 2603 keyboard assembly had a TrackPoint II pointing stick with the mouse buttons uniquely placed on the front of the laptop. The only FRU number known is 59G7920 for a US English keyboard^[52][52]
IBM - IBM Mobile Systems Hardware Maintenance Manual Volume 1 (#S82G-1501-01) [accessed 2023-07-13].. The keyboard assembly's colour palette is the same as the PS/note 182 series' Model M6 with its deep blue numeric keypad overlay and various gold keycap legends.

IBM ThinkPad 750 series (1993), 755C series (1994) & 370C (1995)

Summary: Type V Model M6-1, black skeletal or solid barrel slider, TrackPoint II pointing stick, made by Lexmark & Key Tronic

The IBM 9545 ThinkPad 750 series were mostly 33MHz Intel 486SL-based successors to the IBM ThinkPad 700 and 720 series announced on the 8th September 1993. The 750 (9.5" monochrome DSTN display), 750C (10.4" colour TFT) and 750P (convertible 9.5" monochrome DSTN with pen support) were launched the same day they were announced, with 750Cs (9.5" colour DSTN) following on 30th November 1993^[21][21]
IBM - IBM ThinkPad 750, 750Cs, 750C and 750P Systems and Related Optional Features Brief Description of Announcement, Charges, and Availability (#193-269) [accessed 2023-06-25].. The last 750 series laptop, 750Ce, was uniquely an i486DX2/50 based 10.4" colour TFT follow-up seen in the press by February 1994^[55][55]
InfoWorld - 7 Feb 1994 [accessed 2023-05-26]. License/note: accessed via Google Books. and launched in June^[56][56]
ThinkWiki - ThinkPad History [accessed 2023-05-14].. The IBM 9545 ThinkPad 755C (10.4" TFT) and 755Cs (9.5" DSTN) were announced on 17th May 1994 and based on the 750 series (hence using the same type number) but with either a 50MHz IntelDX2 or 75MHz IntelDX4 CPU^[57][57]
IBM - IBM ThinkPad 755C and 755Cs, Traveling Multimedia for IBM ThinkPad 755C, and ThinkPad 340MB Hard Disk for ThinkPad 700/700C/720/720C Brief Description of Announcement, Charges, and Availability (#194-168) [accessed 2023-07-13].. The IBM 9545 ThinkPad 370C was a singular release based on the 755C series (hence again the same type number) but with a 75MHz IntelDX4 CPU announced and launched on 9th May 1995^[58][58]
IBM - IBM ThinkPad 370C Brief Description of Announcement, Charges, and Availability (#LG95-0074) [accessed 2023-07-13].. The original four 750 laptops were withdrawn in September 1994^[59][59]
Wikipedia - IBM ThinkPad 750 [accessed 2023-05-26].. The DX2 and DX4 755C and 755Cs were withdrawn effective 8th December 1995^[60][60]
IBM - Withdrawal From Marketing: Selected ThinkPad Systems and Options (#A95-1314) [accessed 2023-07-13]. and 20th August 1996^[61][61]
IBM - Options by IBM Withdrawal: Selected PC Products -- Replacements Available (#996-214) [accessed 2023-07-13]. respectively. The 370C was withdrawn from marketing effective 28th October 1996^[62][62]
IBM - Withdrawal From Marketing: Selected ThinkPad Systems (#A96-557) [accessed 2023-06-24]..

At the 750 series' launch, they were the first hosts to a Type V Model M6-1 keyboard assembly. Those and specifically 755C and 755Cs and 370C have the same keyboards and for the most part have a 66G01xx part and FRU number nomenclature except the German black (FRU 66G6402) and Russian (FRU 85G7443) variants^[63][63]
IBM - IBM Mobile Systems Hardware Maintenance Manual Volume 2 (#S82G-1502-03) [accessed 2023-07-13].. Very late Key Tronic made examples have been seen with 39H40xx part number nomenclature too^[64][64]
ASK Keyboard Archive - P/N 39H4027 (1996, Key-Tronic) [accessed 2023-06-23]. License/note: photos saved from volatile eBay listing.. Being the first bearers of the original Type V ("V(A)"), the 750s introduced the concept of using the keyboard as a convenient lid to the laptop's base to ThinkPads by having the keyboard be attached to the laptop through two hinges and two slide locks. Characteristic of the early 9545 keyboard assemblies were the thin and entirely red mouse buttons for the TrackPoint II pointing stick. The singular physical layout change between the 9545 keyboard assembly and the keyboards found on the ThinkPad 700 and 720 series was the added Fn key in the bottom-leftmost corner. The Fn key is used to access several new hotkey functions represented by dull light blue sublegends across various F-keys. Like the PS/55 note C52 keyboard, Japanese layout 750/755C/370C keyboards had their arrow keys shifted to in between the right Alt and Ctrl keys. Still present compared to 700/720 keyboards are the dull blue overlay numeric keypad and [dull] gold modifier, lock and utility key legends. A grey version of specifically the ThinkPad 750 series was also made in an overall grey case with a matching keyboard with grey keycaps for Germany (keyboard FRU 66G0152) and France (FRU presently unknown). This keyboard assembly can be referred to as the "early 9545 keyboard assembly" to contrast it with its Type V(B) late 9545 successor.

Lexmark GS20 OEM series (1993)

Summary: Type II Model M6, [presumably] brown skeletal barrel slider, FSR pointing stick, made by Lexmark

The Lexmark GS20 was a series of laptops produced by Lexmark for their own Lexbook branding and to serve as a template for laptops for other companies to brand. It was a sister laptop to the earlier AR10 series. No third-party branded GS20s have been [re]discovered yet, but the GS20 began appearing in Lexmark's advertising by November 1993^[65][65]
PC Mag - 23 Nov 1993 [accessed 2023-05-11]. License/note: accessed via Google Books. and self-branded Lexmark Lexbook GS20s were available by March 1994^[35][35]
Computer Business Review (CBR) - Lexmark launches Lexbook end-user portable line [accessed 2023-05-11]..

The keyboard assembly itself was branded the Lexmark Notebook Keyboard with Integrated Pointing Stick and was used extensively in advertising Lexmark's keyboard portfolio alongside the AR10's keyboard assembly. Like the AR10 keyboard assembly, the GS20 keyboard has all the technical traits of a Model M6 but it resembled an intermediary between M6s such as the IBM PS/2 CL57SX's that looked basically the same as the earlier Model M3 found on the IBM PS/2 L40SX from the outside, and familiar classic IBM ThinkPad 'true' M6s and M6-1s. The single observable difference between the AR10 and GS20 keyboards was their titular use of a 16mm trackball and pointing stick respectively. The GS20 keyboard assembly has a ThinkPad-like 7-row layout that ThinkPads are well known for but retains the smaller square keys around the main alphanumeric and modifier keys section that was characteristic of the M3 and Type I M6s. In that regard, it seems the AR10/GS20 keyboard assembly design also served as the basis for various IBM-branded M6s such as the PS/note 182's, ThinkPad 350's and PS/note 425's. The arrow keys are shifted to the left, which on the AR10 keyboard assembly allowed for space for a trackball (but presumably the GS20 retains this feature so both keyboard assemblies can share some tooling and membrane assembly design commonality). The mouse buttons were placed in between the left Ctrl and Alt keys and labelled as "M1" and "M2", which use mouse button type IBM buckling sleeves. No part numbers have been found for this keyboard. Its keycaps are white and grey, differing from IBM's classic pearl and pebble keycaps as Lexmark used chromatically cooler colours. An overlay numeric keypad is present and appears to be blue from the limited photos available.

Lexmark Lexbook MB10 & MB15 (1993)

Summary: Type IV Model M6-1, black skeletal barrel slider, mouse-key pointing device, made by Lexmark

The Lexmark Lexbook MB10 and MB15 were two subnotebooks Lexmark designed in collaboration with Chips and Technology and originally intended for the OEM market. Under the original name "MiniBook", work on the MB1X series began as early as November 1992^[66][66]
Computer Business Review (CBR) - Lexmark, Chips & Tech team on OEM notebooks [accessed 2023-05-12]. and by December 1992 were expected to be released early 1993^[67][67]
Peter H. Lewis @ The New York Times - The Executive Computer; Is There a Sub-Subnotebook in Your Future? [accessed 2023-05-12].. They finally appeared in marketing by November 1993^[65][65]
PC Mag - 23 Nov 1993 [accessed 2023-05-11]. License/note: accessed via Google Books. and have since been referred to as Lexbooks like their other laptops (the "MB" in the model name is believed to be a remnant of the earlier "MiniBook" name^[68][68]
tankraider - Lexmark Lexbook MB15 [accessed 2023-05-12].). The MB1X series run MS-DOS 5.00 from ROM and used Chips and Technology F8680 packages (an 8086 compatible system-on-a-chip CPU and GPU combo with direct PCMCIA access). The difference between MB10 and MB15 seems to be up for debate but possibly has to do with RAM amount^[69][69]
tankraider - Lexmark Lexbook MB10 [accessed 2023-05-12]..

The MB1X keyboard assembly was branded the Lexmark Notebook Keyboard with Integrated Mouse Key and was clearly related to the IBM ThinkPad 500's Model M6-1, though the layout has been significantly modified. Gone are the small cluster of half-depth keys in the bottom-right corner that the ThinkPad 500 and later 510 were known for, along with two function keys in the top row. Instead of a TrackPoint pointing stick, Lexmark added a "mouse-key" in the bottom-right corner that acts as a joystick-like pointing device. Like Lexmark's AR10 and GS20 designs, two mouse button keys are present in between the Ctrl and Alt keys. Like the ThinkPad 500 and 510 keyboards, the MB1X's M6-1 had medium gauge IBM buckling sleeves for all keys except the top function row, which uses small gauge sleeves instead. No part numbers for MB1X keyboard assemblies are presently known. The keycaps' colour palette was consistent with that of other Lexmark-brand M6 family keyboard assemblies, having grey and white keycaps and vibrant blue overlay numeric keypad legends.

Tadpole SPARCbook 3 series (1994), P1000 series, ALPHAbook 1 (1995) & SPARCbook 3000 series (1997)

Summary: Type III Model M6-1, black solid barrel slider, TrackPoint II pointing stick, made by Lexmark & Key-Tronic

Tadpole was a specialised computer manufacturer originally from Cambridge, England that was for a time in the mid-'90s at least partially affiliated with IBM. The Tadpole SPARCbook 3 series were SPARC-based portable workstations first introduced in late February 1994, initially consisting of the 50MHz microSparc-based SPARCbook 3 (active matrix display, 16-bit audio and 2MB V-RAM) and 3LC (monochrome display and 1MB V-RAM)^[72][72]
InfoWorld - 21 Feb 1994 [accessed 2023-06-27]. License/note: accessed via Google Books.. By 24th July 1995, the 110MHz microSparc-II based 3GX started shipping^[73][73]
InfoWorld - 24 Jul 1995 [accessed 2023-06-27]. License/note: accessed via Google Books.. Sometime before 1998, the 3TX was released with a 170MHz turboSPARC processor^[70][70]
MCbx Old Computer Collection - Tadpole Sparcbook 3TX [accessed 2023-06-26]. License/note: CC BY-NC-SA 3.0.. By July 1995, Tadpole released a Pentium counterpart called the P1000 series that strongly resembled the SPARCbook 3 series. The P1000 series consisted of the P1000 proper (100MHz CPU, 640x480 display)^[74][74]
The Centre for Computing History - Tadpole P1000 Prototype [accessed 2023-06-27]., P1000G (100MHz CPU, 800x600 display)^[75][75]
The Centre for Computing History - Tadpole P1000G [accessed 2023-06-27]. and P1300 (133MHz CPU, 800x600 display)^[76][76]
Computer Business Review (CBR) - TADPOLE DULY LAUNCHES ITS P1300, SPARCBOOK, DOCKING STATIONS [accessed 2023-06-27]. License/note: retrieved via Wayback Machine (2024-05-01 capture).. On 4th December 1995, Tadpole announced the DEC Alpha 21066A-based ALPHAbook 1 which was likewise another counterpart that resembled their other period laptops^[77][77]
Wikipedia - Tadpole Computer [accessed 2023-06-27].. Finally, in 1997, Tadpole introduced the SPARCbook 3000 series that included the 170MHz Fujitsu TurboSPARC-based 3000ST (10.4" display) and 3000XT (12.1" 1024x768 display)^[78][78]
SunExpert - Volume 8, Issues 7–12 [accessed 2023-06-27]. License/note: accessed via Google Books..

All the aforementioned Tadpole laptops use the same keyboard assembly design, which is a particularly late revival and continuation of the IBM ThinkPad 700/720 series' Type III Model M6 keyboard assembly. Tadpole retained the same basic keyboard assembly as evidenced by their base plate hooks remaining in the exact same places as the former ThinkPads' keyboards, but notably, the keyboard has been given a third mouse button. The keyboard has also been 'uprated' to an M6-1 as evidenced by the presence of black barrel sliders reinforced by the "M6-1" designation present on Lexmark-made examples. The limited photos available of their pointing sticks without nub caps present suggest they had TrackPoint II pointing sticks. When Key Tronic took over production, the "M6-1" designation was seemingly dropped despite nothing else changing. Possible part number nomenclature isn't presently understood, with the US English P/N 600515-US currently being the only confirmed part number for a Tadpole M6-1 keyboard assembly. Due to its ThinkPad 700/720 origins, the Tadpole M6-1 keyboard lacks an Fn key and still had a 1-unit sized separation between the left Ctrl and Alt keys, unlike the 700/720's 750 series successor that was released in the interim between the 700/720 series and these Tadpole laptops. The Tadpole M6-1 keyboard also retains green Alt and SysRq legends and a dull blue overlay numeric keypad legends. The Tadpole M6-1 keyboard assembly was screwed onto the bottom of the laptop's base unit top case piece.

Lexmark Lexbook SE10 (1994)

Summary: Type IV Model M6-1, [presumably] black skeletal barrel slider, mouse-key pointing device, made by Lexmark

The Lexmark Lexbook SE10 was a 50MHz IBM 486SLC2 powered monochrome display subnotebook running MS-DOS and Windows made available by March 1994^[35][35]
Computer Business Review (CBR) - Lexmark launches Lexbook end-user portable line [accessed 2023-05-11].. It's possible this laptop was in development as early as 1992 as a currently unseen prototype Lexmark/Western Digital subnotebook called "Enchilada" with similar specifications - same 50MHz 486SLC2 CPU, same class of notebook laptop, similar weight (4lbs/~1.8kg versus 3.5lbs/~1.6kg) - was demonstrated at COMDEX/Fall '92. If they're related, the "E" in "SE" may refer to "Enchilada"^[67][67]
Peter H. Lewis @ The New York Times - The Executive Computer; Is There a Sub-Subnotebook in Your Future? [accessed 2023-05-12]..

The SE10 keyboard assembly was a variant of the Lexmark Notebook Keyboard with Integrated Mouse Key the Lexmark Lexbook MB1X series first used, and by extension is related to other Type IV Model M6-1 designs such as the IBM ThinkPad 500 and 510 keyboard assemblies. The physical layout in fact had design traits from both the MB1X and ThinkPad 500 designs; it had a "mouse-key" pointing device in the bottom corner, full-size arrow keys and two mouse button keys in between the Ctrl and Alt keys like an MB1X keyboard assembly, but also had no gaps in between keys on the top half-depth key row like a ThinkPad 500/510 keyboard assembly. Due to this and the host laptop's specifications, it's possible SE10 and ThinkPad 500s were more intimately related than is disclosed by the companies. Like the other Type IV laptop keyboard assemblies, the SE10 version had medium gauge IBM buckling sleeves for all keys except the top function row, which uses small gauge sleeves instead. No part numbers are presently known. To match the host laptop, the SE10 keyboard assembly was dark grey (more so than IBM/Lexmark pebble-coloured grey keycaps) and had no two-tone colour scheme. The overlay numeric keypad legends were vibrant blue though.

IBM RS/6000 Notebook N40 (1994)

Summary: Type III Model M6-1, [presumably] black solid barrel slider, TrackPoint II pointing stick, made by Lexmark

The IBM 7007 RISC System/6000 Notebook N40 was a 50MHz PowerPC 601 based portable workstation with a 1280x1024 resolution screen announced and released on 8th March 1994 and 25th March 1994 respectively, withdrawn from marketing on 19th September 1995, and service was discontinued on 30th June 1997^[80][80]
IBM - US - IBM RS/6000 Model N40 Sales Manual (#7007-N40) [accessed 2023-07-02].. The 7007 was developed by Tadpole Technology for IBM^[81][81]
ibmfiles - IBM RS/6000 N40 Information and Software [accessed 2023-07-02]..

Due to its shared origin with period Tadpole laptops, the 7007 keyboard assembly was virtually identical to that found on them. It's an evolution of the IBM ThinkPad 700/720 series' Type III Model M6 keyboard assembly that was 'uprated' to M6-1 standards and given a third mouse button. Whilst there are presently no photos of the keyboard's base plate and rear label, it has been confirmed it's a "Model M6" family keyboard made by Lexmark and the US English variant's part number is 1403213^[82][82]
Ardent Tool - 7007-N40 [accessed 2023-07-02].. They sported TrackPoint II pointing sticks^[80][80]
IBM - US - IBM RS/6000 Model N40 Sales Manual (#7007-N40) [accessed 2023-07-02].. Thanks to its ThinkPad 700/720 origins, the keyboard lacked an Fn key and still had a 1-unit sized separation between the left Ctrl and Alt keys, unlike the 700's/720's 750 series successor that was released in the interim between the 700/720 series and the 7007. Unlike its Tadpole counterpart, the 7007 keyboard assembly additionally had more vibrant gold modifier, lock and utility key legends. The 7007 keyboard assembly retained green Alt and SysRq and dull blue overlay numeric keypad legends. The only physical difference between the 7007 and Tadpole M6-1 keyboard assemblies was the differing overall mouse button shapes. The 7007 keyboard assembly was presumably screwed onto the bottom of the laptop's base unit top case piece, like its Tadpole counterpart.

IBM ThinkPad 355 & 360 series (1994)

Summary: Type V Model M6-1, black solid barrel slider, TrackPoint II pointing stick, made by Lexmark

The IBM 2620 ThinkPad 360 series were a family of originally Intel 486SX (33MHz) notebooks introduced in EMEA on 17th May 1994 for models 360 (9.5" monochrome STN display) and 360Cs (9.5" STN dual scan) and 24th June 1994 for models 360C (8.4" TFT) and 360P (convertible 9.5" STN dual scan with pen support)^[83][83]
IBM - IBM ThinkPad 360 Family Announcement Letter (#ZG94-0274) [accessed 2023-05-15].. On 17th October 1994 in both US and EMEA, the 360CE (TFT display) and 360CSE (STN dual scan) were introduced with Intel 486DX2 (50MHz) CPUs^[84][84]
IBM - IBM ThinkPad 360CE and 360CSE Announcement (#194-353) [accessed 2023-05-15].^[85][85]
IBM - IBM ThinkPad 360CE and 360CSE Announcement Letter (#ZG94-0520) [accessed 2023-05-15].. Finally, the 360PE was introduced on 28th April 1995 in EMEA as a version of the 360P with a 486DX2 CPU^[86][86]
IBM - IBM ThinkPad 360PE Announcement Letter (#ZG95-0182) [accessed 2023-07-13].. The IBM 2619 ThinkPad 355 series were family of Intel 486SX only notebooks introduced in June 1994^[56][56]
ThinkWiki - ThinkPad History [accessed 2023-05-14]. with models 355 (9.5" monochrome STN display)^[87][87]
ThinkWiki - Category:355 [accessed 2023-05-14]., 355C (8.4" TFT)^[88][88]
ThinkWiki - Category:355CS [accessed 2023-05-14]. and 355CS^[88][88]
ThinkWiki - Category:355CS [accessed 2023-05-14].. All IBM 2619s and the 2620 models 360 and some 360Cs configurations were withdrawn from marketing effective 8th December 1995^[60][60]
IBM - Withdrawal From Marketing: Selected ThinkPad Systems and Options (#A95-1314) [accessed 2023-07-13].. The 360CE, remaining 360Cs configurations, 360CSE and 360P were withdrawn effective 21st December 1995^[89][89]
IBM - Hardware Withdrawal: Selected ThinkPad Systems (#995-123) [accessed 2023-07-13].. The 360PE was finally withdrawn effective 28th October 1996^[62][62]
IBM - Withdrawal From Marketing: Selected ThinkPad Systems (#A96-557) [accessed 2023-06-24]..

The 2619/2620 keyboard assembly was the introduction of the Model M6-1 for the ThinkPad 300 market segment and was the same as the IBM ThinkPad 750/755C/370C keyboard assembly. Being a Type V design, the keyboard assembly was indeed hinged to allow it to lift to give access to major system components. Also characteristic were the thin and entirely red mouse buttons for the TrackPoint II pointing stick. Both 355s and 360s shared the same keyboard assembly part and FRU number pool with 84G5xxx nomenclature^[63][63]
IBM - IBM Mobile Systems Hardware Maintenance Manual Volume 2 (#S82G-1502-03) [accessed 2023-07-13].. The Japanese version of this keyboard has its arrow keys shifted to in between the right Alt and Ctrl keys. The keyboard retains the dull blue overlay numeric keypad and hotkey sublegends and dull gold modifier, lock and utility key legends from its 750/755C/370C origins.

Winbook XP series (1994)

Summary: Type VI Model M6-1, black solid barrel slider, FSR pointing stick, made by Lexmark

The Winbook XP (no relation to Microsoft or Windows XP) series was a family of laptops from Winbook Computer Corporation. The Winbook XP proper was marketed from at least the end of May 1994 and had a 75MHz IntelDX4 CPU^[22][22]
InfoWorld - 31 May 1994 [accessed 2023-05-14]. License/note: accessed via Google Books.. This was followed by the XP5 by November 1995 with either a 75MHz or 90MHz Intel Pentium CPU^[90][90]
InfoWorld - 6 Nov 1995 [accessed 2023-05-14]. License/note: accessed via Google Books..

These XP series laptops used a Model M6-1 based keyboard assembly made by Lexmark for Winbook that in physical layout resembled the Type IV keyboard assemblies used by the subnotebook IBM ThinkPad 500 series and Lexmark Lexbook MB1X series (etc.) but was in fact the beginning of its own keyboard sub-series - the Type VI. The Winbook XP/XP5 keyboard assembly also had 6 rows of keys, but it's an overall larger keyboard to the aforementioned subnotebooks' keyboards, has an extra 0.25-unit of horizontal key space leading to [amongst other things] enter keys larger than even those on standard full-size keyboards and returns to using standard gauge IBM buckling sleeves for all keys except the top row (which continues to use small gauge sleeves). In marketing, Winbook stated the XP had a "TrackPoint II-like pointing device" but it in fact used a Lexmark-Unicomp FSR pointing stick. In addition to this, XP series laptops could also have a 19mm trackball (XP and XP5) or trackpad (seemingly XP5 only), but these were separate devices from the keyboard assembly itself. Presently, the only known part number is 1403740 for a US English keyboard. The XP series keyboard assembly was reminiscent of a contemporary IBM ThinkPad keyboard with its various dull gold key legends and dull blue overlay numeric keypad sublegends. It additionally had various cyan sublegends and Fn key legend.

AST Ascentia 9X0N series (1994)

Summary: Type VI Model M6-1, black solid barrel slider, TrackPoint II or FSR pointing stick, made by Lexmark

The AST Ascentia 900N series was a family of notebooks from AST Research Inc. first introduced in the week of 13th June 1994 with the AST Ascentia 900N. The 900N was a 50MHz Intel 486DX2 or 75MHz IntelDX4-based laptop^[91][91]
InfoWorld - 13 Jun 1994 [accessed 2023-05-14]. License/note: accessed via Google Books., which was followed by the 910N in February 1995 that was largely the same machine but with an improved battery^[92][92]
InfoWorld - 30 Jan 1995 [accessed 2023-05-14]. License/note: accessed via Google Books.. By late May 1995, the series was joined by the final model - 950N - that was 75MHz Intel Pentium based^[93][93]
InfoWorld - 29 May 1995 [accessed 2023-05-14]. License/note: accessed via Google Books..

The 9X0N series used a Model M6-1 based keyboard assembly made by Lexmark for AST that appears to be a reskin and rehouse of the Winbook XP/XP5's Type VI Model M6-1. As such, it was a 6-row keyboard with standard gauge IBM buckling sleeves in most of the keys except the top row that used small gauge sleeves. The 9X0N keyboard likewise had an extra 0.25 units of horizontal key space leading to [amongst other things] enter keys larger than even those on standard full-size keyboards. Uniquely for a non-IBM keyboard, the 9X0N keyboards could have a TrackPoint II pointing stick, but other examples of the keyboard have been spotted with Lexmark-Unicomp FSR pointing sticks. AST's name for the pointing stick was "SmartPoint"^[94][94]
PC Mag - 5 Dec 1995 [accessed 2023-05-14]. License/note: accessed via Google Books.. Two similar part number nomenclatures - 232010-0xx and 232011-0xx - have been spotted and seem to use TrackPoint or FSR sticks respectively. Additionally, they're given a secondary "Lexmark Number" that was in either the 13788xx or 1482xx ranges. AST keyboards were notable for their green accents, and the 9X0N keyboard assembly was no different with its various green sublegends including numeric keypad overlay and green nub cap.

IBM ThinkPad 510Cs (1994)

Summary: Type IV Model M6-1, black skeletal barrel slider, TrackPoint II pointing stick, made by Lexmark

The IBM 2604 ThinkPad 510Cs was a subnotebook and follow-up to the IBM ThinkPad 500 series introduced on 30th June 1994. The 2604 was available in only one model and was essentially an upgraded ThinkPad 500 with an IBM Blue Lightning 486BL2-50 50/25MHz CPU and colour display^[95][95]
IBM - IBM ThinkPad 510Cs and Features Announcement (#194-214) [accessed 2023-07-13]..

The 2604 keyboard assembly was essentially identical to that of its predecessor except for the added brightness and contrast control legends across the Q and A and W and S keys respectively. It's a Type IV Model M6-1 with their typical traits such as slightly smaller keys compared to most other M6 family keyboards and had medium gauge IBM buckling sleeves for all keys except the top function row with small gauge sleeves instead. Like before, IBM managed to fit almost all the keys of a regular contemporary 7-row ThinkPad keyboard (81 versus the typical 85 ANSI/86 ISO keys) into this footprint, which resulted in some compromises such as the cluster of half-depth keys in the bottom-right corner. The 2604 keyboard assembly had a TrackPoint II pointing stick with the mouse buttons uniquely placed on the front of the laptop. The only FRU number known is 73G3394 for a US English keyboard^[52][52]
IBM - IBM Mobile Systems Hardware Maintenance Manual Volume 1 (#S82G-1501-01) [accessed 2023-07-13].. This keyboard assembly's colour palette is again unchanged with its deep blue numeric keypad overlay and various gold keycap legends.

IBM ThinkPad 755CD/755CDV/755CE/755CSE/755CV/755CX series (1994)

Summary: Type V Model M6-1, solid barrel slider, TrackPoint III pointing stick, made by Lexmark & Key Tronic

The IBM 9545 ThinkPad 755CD/755CDV/755CE/755CSE/755CV/755CX (aka, "late 755C") series was a follow-up to the original IBM ThinkPad 755C series. The 100MHz IntelDX4-based 755CE (10.4" TFT 640x480 display), 755CD (10.4" TFT 640x480 with enhanced audio and CD-ROM drive) and 755CSE (10.4" DSTN 640x480) were announced first on 17th October 1994 and made available on the same day, 31st October and 17th November 1994 respectively^[96][96]
IBM - IBM ThinkPad 755CE, 755CSE, and 755CD Announcement (#194-352) [accessed 2023-06-25].. On 9th May 1995, the 75MHz Intel Pentium based 755CX (10.4" TFT 640x480/800x600) was introduced^[97][97]
IBM - IBM ThinkPad 755CX Introduces SVGA Display and Pentium Processor Announcement (#195-131) [accessed 2023-06-25].. This was followed by the 100MHz IntelDX4 based (upgradable to 75MHz Intel Pentium) 755CV (without CD-ROM drive) and 755CDV (with CD-ROM drive) introduced on 31st May and 20th June 1995 respectively, which both had overhead projector capability thanks to a removable panel behind their LCDs^[98][98]
IBM - IBM ThinkPad 755CV Features Overhead Projection Capability Announcement (#195-133) [accessed 2023-06-25].^[99][99]
IBM - IBM ThinkPad 755CDV Features CD-ROM and Overhead Projection Capability Announcement (#195-216) [accessed 2023-06-25].. Finally, on 5th September 1995, 75MHz Intel Pentium versions of the 755CD were introduced^[100][100]
IBM - IBM ThinkPad 755CD Pentium Models Announcement Letter (#A95-1025) [accessed 2023-06-25].. Like previous 755C series ThinkPads, all of these newer laptops were also only available with colour displays. The 755CD, 755CDV, 755CE, 755CV and 755CX were withdrawn from marketing effective 28th October 1996^[62][62]
IBM - Withdrawal From Marketing: Selected ThinkPad Systems (#A96-557) [accessed 2023-06-24]..

The late 9545 keyboard assembly was a revision of the original IBM ThinkPad 750C/early 755C/370C Type V Model M6-1 keyboard assembly, additionally designated "Type V(B)" to distinguish it from its earlier counterpart. They largely resembled their "Type V(A)" predecessors in that they were M6 family keyboard assemblies that attached to their host laptop through two hinges and two slide locks and could be lifted as a convenient lid to the laptop's base, however, Type V(B) replaced the previously thin and entirely red mouse buttons for larger slide-locking mouse buttons with a thin red decal. This function was also called "drag lock" and could be used to keep the mouse buttons in a pressed state to help with dragging GUI items^[101][101]
David Hill - Tweet 1669677242824237057 [accessed 2023-06-16].. The late 9545 keyboard assembly had an FRU number nomenclature of 84G6xxx^[63][63]
IBM - IBM Mobile Systems Hardware Maintenance Manual Volume 2 (#S82G-1502-03) [accessed 2023-07-13]., though there were several part number nomenclatures used. When they were first manufactured by Lexmark, the part number could be within ranges 29H87xx or 84G6xxx, but when Key Tronic took over production, they used a 39H40xx range just like Key Tronic versions of their 66G01xx FRU 750/early 755C/370C series (early 9545 keyboard assembly) predecessors. Like its predecessor, the Japanese version of the late 9545 keyboard assembly had their arrow keys shifted to in between the right Alt and Ctrl keys. Also still present were the dull blue overlay numeric keypad and dull gold modifier, lock and utility key legends. Unlike its predecessor, there were no grey-coloured versions of the late 9545 keyboard assembly available for French and German laptops.

IBM ThinkPad Power Series 850 (1995) & RS/6000 Notebook 860 (1996)

Summary: Type V Model M6-1, black solid barrel slider, TrackPoint III pointing stick, made by Lexmark or Key Tronic

The IBM 6042 ThinkPad Power Series 850 and IBM 7249 RS/6000 Notebook 860 were two PowerPC 603e based laptops apart of a series that succeeded the earlier IBM RS/6000 Notebook N40. The 6042 had a 100MHz CPU and was announced in June 1995 and then made available on 9th September 1995^[103][103]
IBM - IBM ThinkPad Power Series 850 and Supporting Options Announcement (#A95-768) [accessed 2023-07-13].. The 7249 had a 166MHz CPU and was announced on 8th October 1996 and made available on 8th November 1996^[104][104]
IBM - IBM RS/6000 Notebook 860 Announcement (#196-248) [accessed 2023-07-13].. The 6042 and 7249 were withdrawn on 20th March 1996 and 30th January 1998 respectively^[105][105]
Wikipedia - IBM ThinkPad Power Series [accessed 2023-05-25]..

Both machines use the same Type V Model M6-1 keyboard assembly with a TrackPoint III pointing stick. Compared to its 'consumer' ThinkPad counterparts for late 755C series and 365 series, the 6042/7249 keyboard assembly lacked an Fn key and many sublegends an Fn key would normally access on other laptops (in this regard, the layout resembled the earlier Type III M6 family keyboard assemblies instead). This keyboard assembly also had slide-locking mouse buttons, but they're a different shape to other Type V(B) M6-1s' mouse buttons. To match the footprint of the laptop's base, the frame of this keyboard was also larger than other Type Vs. As confirmed by cross-referencing the 850's Hardware Maintenance Manual and known photos of 860 keyboards' rear labels, 850 and 860 share the same pool of keyboards with 29H81xx FRU number nomenclature^[106][106]
IBM - IBM ThinkPad Power Series 850 Hardware Maintenance Manual (#S30H-2383-00) [accessed 2023-07-13]. License/note: document scanned by OS/2 Museum (M. Necasek).. They could also have 45H87xx nomenclature part numbers. The 6042/7249 keyboard assembly's legend colour variation was fairly tame with even the overlay numeric keypad using white legends, though the Alt keys remain green.

IBM ThinkPad 365 series (1995)

Summary: Type V Model M6-1, black solid barrel slider, TrackPoint III pointing stick, made by Lexmark or Key Tronic

The IBM 2625 ThinkPad 365 series were a family of Cyrix 4x86, 5x86 and Intel Pentium notebooks. The original 365C family with 75MHz Cyrix Cx486 CPUs launched on 17th November (for SelectaSystem versions with either PC DOS 7.0, OS/2 Warp 3 or Windows 3.11) or 1st December 1995 (for Windows 95) with the 365C proper (TFT display, no ESS1688 audio controller), 365CS (DSTN, no ESS1688), 365CD (TFT, ESS1688) and 365CSD (DTSN, ESS1688)^[107][107]
IBM - IBM ThinkPad 365C/CS/CD/CSD Announcement Letter (#A95-1331) [accessed 2023-07-13].. IBM then introduced the 100MHz 5x86 based 365ED (with ESS1688) and 365E (no ESS1688) on 21st May and 27th June 1996 respectively^[108][108]
IBM - IBM ThinkPad 365E and 365ED Announcement Letter (#A96-302) [accessed 2023-07-13].. Finally, IBM released the Pentium 100MHz or 120MHz based 365X (no CD-ROM drive) and 365XD (with CD-ROM drive) on either 21st June 1996 or 28th June 1996 depending on configuration^[109][109]
IBM - IBM ThinkPad 365X/365XD Announcement Letter (#A96-303) [accessed 2023-07-13].. The 365 family was withdrawn in June 1996 (365C), October 1996 (365E) and October 1997 (365X)^[110][110]
Wikipedia - IBM ThinkPad 365 [accessed 2023-05-26]..

All 365 series laptops used a Type V Model M6-1 keyboard assembly that was identical to the late IBM 9545 Type V(B) M6-1 design. As such, the 2625 keyboard assembly had a TrackPoint III pointing stick, was hinged and slide-locking mouse buttons. The Japanese version of the keyboard had its arrow keys shifted to in between the right Alt and Ctrl keys. 365 series keyboard assemblies usually had a 42H39xx part and FRU number nomenclature but the US English keyboard (FRU 41H9789) and Swiss French and German combination keyboard (FRU 75H7562) were notable exceptions^[111][111]
IBM - IBM Mobile Systems Hardware Maintenance Manual Volume 3 (#S82G-1503-05) [accessed 2023-07-13].. Additionally, a 12J194x FRU number nomenclature has been observed but no IBM documentation about them has been found thus far. The 2625 keyboard assembly's legend colours were also inherited from the late 9545 keyboard assembly and Key Tronic OEM examples had notably dull gold modifier, lock and utility key legends and white overlay numeric keypad legends, though the Alt and SysRq key legends remain green. The 2625 was the last Model M6 family laptop keyboard release, with the youngest example observed from May 1999^[1][1]
u/themavery - A NOS IBM Model M6-1 ThinkPad 365 Keyboard Assembly [accessed 2023-06-27]..

Apple Newton MessagePage Keyboard (1996)

Summary: Type IV Model M6-1, black solid barrel slider, no integrated pointing device, made by Key Tronic

Please see the Apple Newton Keyboard - The time Apple turned to IBM/Lexmark for a Model M article for information on the Apple Newton MessagePad Keyboard (model X0044). The X0044 will soon have its own separate ASK Wiki page.

Part number list

199 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.

Gallery

Icons

These icons are designed to present overall style only. Due to the limitations of pixel art resolution, the keys' unit sizes and spacing between them, bezels, etc. may not be accurately reproduced. Relative scaling between different icons may also not be accurate.

Further reading & resources

Internal

External

Sources

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

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