The IBM Enhanced Keyboard turns 40

On this day, in 1985, IBM announced the 7531 and 7532 Industrial Computers. Two AT-derived computers that were "designed for information-handling applications in industrial plant floor environments". The announcement letters only lightly touched on their keyboards, noting their bidirectional serial interface, mode indicators and separated typewriter and numeric keypad sections - all inherent to any AT-based keyboard. But this keyboard was actually so much more than what was led on. IBM worked to enhance them, aptly calling them... the Enhanced Keyboard. Today, we now see these as the quintessential Model M despite not being the only Model M nor even the first. I have written this crash course of sorts on the subject entirely this afternoon to help us celebrate!

Contents

The beginning

First, let's get something out of the way. If you are familiar with Model Ms, you may already known the IBM 3161 and 3163 ASCII Display Stations were the first to release an Enhanced Keyboard. 3161 and 3163 were announced on 18^th June 1985 and slated for a release the following month^[1][1]
IBM - IBM 3161 and IBM 3163 ASCII Display Stations Models 11 and 12 Brief Description of Announcement, Charges, and Availability (#185-078) [accessed 2025-05-21]., whereas 7531 and 7532 were announced on 21^st May 1985 and slated for a release in Q4 1985.^[2][2]
IBM - IBM 7531 Industrial Computer Brief Description of Announcement, Charges, and Availability (#185-053) [accessed 2025-05-21].^[3][3]
IBM - IBM 7532 Industrial Computer Brief Description of Announcement, Charges, and Availability (#185-054) [accessed 2025-05-21]. 753X was announced first, 316X shipped first. To my knowledge, the 7531/7532 announcements were the earliest published reference to this keyboard and thus the beginning of the Enhanced Keyboard timeline.

As of last year, we now know for sure that IBM originally designated the Enhanced Keyboard "Keyboard G"/"Model G" before "Keyboard M"/"Model M" supplanted it as the overall family designation. It was firmly an IBM Lexington, Kentucky keyboard, designed as a "low-cost, high-volume" but still "excellent quality" keyboard compared to a Model F keyboard. The savings were primarily achieved by modifying IBM's primary keyswitch technology of the time - the clicky buckling spring - to be sensed via a membrane assembly rather than a capacitive pad card.^[4][4]
IBM - Lexington Today - New IBM Product Features Lexington Keyboard [accessed 2025-05-21]. License/note: accessed via a deskthority post courtesy of rocco_16v & photo excerpts used under fair dealing. In fact, the 1983 patent by Edwin T. Coleman, III for membrane buckling springs suggests this saving to be about half.^[5][5]
IBM - Rocking switch actuator for a low force membrane contact switch [accessed 2025-05-21]. We have relatively recently observed two potential Enhanced Keyboard prototypes, provisionally known as "October 1984" and "December 1984" based on all observable date codes on them.

Whilst I am sure most agree that the earlier capacitive design is more technically impressive and advantageous, the legacy the keyboard acquired despite that certainly indicates it was not the biggest of deals. The keyboard's legacy should not solely be that it was a cost-saving measure anyway, as it was done in parallel to genuine innovation and new features. The main takeaway from the Enhanced Keyboard is its eponymous Enhanced layout. It is in a lineage that I guess you could call the Base (1977) - Converged (1983) - Enhanced (1985) pipeline, the latter two being IBM 3270-family terminal keyboard designs. IBM's previous major PC keyboard layouts, XT and AT, were instead derived from the IBM 5250 typewriter layout. Versus XT and AT, the Enhanced layout implements:

With only minor modifications such as adding Super (eg, Windows) keys, the Enhanced layout remains the primary keyboard standard today. 40 years and still relevant is quite the achievement.

Some other immediate improvements over the average Model F were making the cable modular thanks to a 6-pin shielded data link (SDL) socket and often a cover set made of PVC plastic that is dyed instead of painted. The SDL socket was only present on PC-compatible Enhanced Keyboards and eventually removed, but a certainly handy feature when present. The dyed PVC is also advantageous, meaning the colour cannot wear off and the texture is more resilient. It also makes the keyboard more flexible, which in my opinion is sort of another bonus - Model Fs may be extremely rigid and taut feeling, but inflexibility may make them more inclined to be brittle if subjected to considerable stress or shock.

What is inside?

A complete sub-assembly (CSA)! Most Model Ms contain a separable keyboard assembly that can be completely removed from the host cover set and operate on its own. From the bottom to the top, it is a sandwich of a base plate, a membrane assembly, a membrane blanket, keyswitch actuators and a keyboard frame.

The keyswitches are the most notable part, of course. The primary actuator design is the aforementioned buckling springs, which buckle a certain way when pressed to pivot a plate to apply pressure on a pair of contact points on the membrane assembly. The design allows the actuation and peak tactile and audible feedback to be matched perfectly. The click is iconic, but it is known to have high ping from spring resonation. The IBM Soft Touch Keyboard is a minor Enhanced Keyboard variant that tried to address it by greasing the springs. The completely non-clicky IBM Basic Keyboard was also introduced with Quiet Touch rubber dome actuators instead.

There is one elephant in the room with most Model Ms though - the rivets. The keyboard frame and base plate are sealed by melting plastic rivets, which can invariably break over time and/or due to environmental factors. It does not always happen, but it can happen, and thus is something to consider should you want to own one of these.

Should they break, you are not out of luck though. People like Brandon (ClickyKeyboards) can repair them for you or you can learn to do so yourself with Bitten's Model M restoration guide. "Bolt mod" and "screw mod" are the relevant keywords.

Continous evolution

The Enhanced Keyboard design did not stay constant. Even just two years after 753X and 316X, IBM was altering the branding and putting the keyboard on a mild diet ready for the IBM Personal System/2 family and 3151 ASCII Display Station releases. Two further diets will be implemented in the '90s.

This was because the keyboard was still quite expensive despite the move to a membrane design. It was after all still an advanced, flagship-level keyboard design that IBM self-designed and originally self-made largely by American and Scottish workforces with their inherent higher cost versus the Far East. Below are some historical US dollar prices versus adjusting for inflation for 2024:

I am sure there is technically someone out there who would pay north of $800 for a brand-new IBM Enhanced Keyboard if they were still making them, but most would not. That price is undigestible today. Remember that computers in general were still not as common nor viewed as a commodity back then as they are nowadays. Computers costed more, thus a larger budget could be afforded to a keyboard. Computers became more popular as the '80s and '90s unfolded and IBM faced intense competition, likely mandating the so-called diets. Model M enthusiasts nomenclature'd these as "generations" of which four are typically recognised. The following summarises them for PC-compatible, pearl white Enhanced Keyboards.

This has led to a general opinion that earlier is better and more desirable. It is essentially hard to argue against that - the earlier keyboards are heavier, more taut and more likely to have a modular cable. I have even tried to balance this out in my buyer's guide. Do not outright dismiss the later ones though. The magic inside the keyboards - the buckling springs - were never intentionally changed. So long as the given keyboard is in good shape, I truly believe any one of the generations gives you amongst the best typing instruments bested only by IBM's earlier creations.

Changing hands & rebrands

In the midst of the diets, parts of the Model M family (including Enhanced Keyboard production) was shuffled about and changed hands a few times. IBM itself continuously produced Model Ms in some form until 2000, but the United States based production got largely divested in the early '90s.

In March 1991, IBM Information Products Corporation (which included IBM's Lexington and Boulder, Colorado typewriter and keyboard operations) was divested to form Lexmark International. A five-year partnership was established, which saw IBM subsequently marketing much of Lexmark's output with "IBM" branding.^[19][19]
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 2025-05-21].^[20][20]
IBM - Archives: 1990s - 1991 [accessed 2025-05-21]. License/note: retrieved via Wayback Machine (2023-08-02 capture). After those five years, a renewal of that relationship was signed that excluded keyboards.^[21][21]
Lexmark - Lexmark International Announces Supplies Trademark Agreement With IBM [accessed 2025-05-21]. License/note: retrieved via Wayback Machine (1998-02-09 capture). For 1994, keyboard sales accounted for 11% of Lexmark's revenue and just 5% of its gross profit, so they threw in the towel by April 1996 to focus on printers.^[22][22]
Clare Goldsberry @ Plastic News - LEXMARK EXITS KEYBOARDS, TARGETS PRINTERS: FIRM TO OUTSOURCE MORE MOLDING [accessed 2025-02-05]. License/note: retrieved via Wayback Machine (2022-08-10 capture). Lexmark employees who were fond of keyboards resigned to form Unicomp to continue Lexington-based keyboard production.

Lexmark called their Enhanced Keyboards "Classic Touch" in reference to their buckling springs being "classic". The overall quality was pegged to IBM-branded ones of the same period, but Lexmark added their own branding. Lexmark and later Unicomp also both indulged in an OEM keyboard business, resulting in some rebranded and modified Enhanced Keyboard variants. Here is a tasty sample of them.

Lexmark ultimately did not need to change much regarding the keyboard's overall design, but Unicomp did. The challenges they faced included the popularity of the Windows key after Windows 95's release, the introduction of USB to simplify how most devices connect to a PC, and beige largely going out of fashion for a while. In October 2000, Unicomp first made Super keys available as an option.^[29][29]
Unicomp - The Customizer Keyboard [accessed 2025-05-21]. Around 2003, they also made raven black cover sets similar to the IBM TrackPoint II Keyboard (Black) available. USB versions finally made an appearance in 2006.

Unicomp calls their Enhanced Keyboard the "Classic" (and formerly the "Customizer"). Unicomp Classics can be compared unfavourably to IBM-branded keyboards by some in both aesthetics and performance. Aesthetics is subjective, so no comment. The keyboard does look quite a bit different though, but its heart is in the right place. In my experience, the key feel can be different, probably due to the known change in membrane blanket material^[30][30]
fohat @ DT - Model M and the rubber sheet, better without? [accessed 2025-05-21]. but it is still distinctly a Model M experience. I must reference value through a perspective I often give. The difference in such between IBM's highest ($844) and Unicomp's lowest ($144) is staggering, but it does not translate into the Unicomp Classic being six times worse. Far from it. I think IBM, Lexmark and Unicomp generally did a good job preserving the core typing experience from all the cuts and tweaks over 40 years of production.

Legacy

Well, you know I like them. Hopefully, it is quite apparent the enthusiasm I have for them. The Enhanced Keyboard, the raw impact its layout had, and the enduring staying power is legendary. Unsurprisingly, the keyboard design that managed to survive 40 years has a reputation. Here are some other opinions on them.

If you are completely new, I understand if you do not want to rely on any of these words alone. I encourage you to give one a try for yourself. For Model Ms in general, I maintain a buyer's guide you can check out to get started in this journey. If you have keyboard conventions and meetups in your area, perhaps register your interest and ask in any associated communities if someone can bring an Enhanced Keyboard with them for you to sample? My associated communities such as /r/modelm and the IBM Keyboards Discord stand ready to assist if needed and are both welcoming places to explore and learn more about IBM and family keyboards!

Further reading & resources

Sources

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