Model G as the original designation for Model M & the existence of Models 1A and 1B

It has been theorised for a while that the IBM Model M keyboard family originally bore the designation "G". This was based on some limited documentation evidence combined with the fact that "G" comes after "F" in the English alphabet (obviously). On 19th May 2024, a user on deskthority posted the most telling evidence to date that the Model M started out as "G". In the quest to find out more, I found a lot of supporting evidence for a "Model 1A" (122-key Model M Converged Keyboard) and a "Model 1B" (104-key Quiet Touch Keyboard) as well. Things obvious in hindsight and perhaps some people are already aware of them, but I thought it would be useful to present my findings. Naturally, this has interesting implications for Admiral Shark's Keyboards and perhaps is interesting to the wider (vintage) computing and keyboard community.

Special thanks to the following for their contributions during this research and/or making available the pieces of the puzzle used to complete this article: BittenEite, Howard81, hypkx, Jugostran, rocco_16v and t4teeee.



At least in internal communication and documentation, IBM referred to major keyboard designs as "Keyboard insert letter" since the 1970s. ASK has the following understanding:

* Further research is required. I personally also suspect it might refer to IBM Elastic Diaphragm encoded keyboards as they were IBM's first family of keyboards using a named key-switch design.

In marketing speak for consumers and businesses, IBM seldom used "Keyboard" nomenclature, but the backs of various keyboards may have a rear label that reveals the designation as "Model insert letter" (not to be confused with later OEM-specific model numbers like "SK-8835"). This was most prominent for Model M keyboards, but many Model F keyboards also stated what they were (at least for USA-made ones on the internal assembly rear label if not the outer rear label). Based on the fact both the "Keyboard" and "Model" designations for both Fs and Ms are the same, ASK also presently assumes "Keyboard" and "Model" were the same thing in IBM's eyes. Here are some examples of such telling "birth certificates":

See Keyboard Rear Labels for even more examples of the above

As for what meets the requirement for a unique lettered designation, it's unknown and unconfirmed by literature, but we can make some assumptions. The most well-documented models - B, F and M - are major keyboard families spanning many markets, layouts, and even whether a given member is physically integrated into a larger host system or not. For Model Ms, they don't even all use the same key-switch. As such, I tend to regard a "Model x" as signifying an IBM flagship universal keyboard platform based on at least one overarching technology for a given era/generation.

For Bs and Fs, their use of IBM beam spring and IBM capacitive buckling spring key-switches respectively are very obvious shared characteristics. A buckling-spring 101-key IBM Enhanced Keyboard (Model M) or a buckling-sleeve IBM ThinkPad Keyboard (Model M6/M6-1) may seem very different on the surface, but what ties them together is that they are clearly both intended to be IBM's best keyboard offering for their respective markets' (desktop computing and portable computing respectively) flagship computing devices (Personal System/2 and ThinkPad respectively) and their use of a membrane assembly. Whilst not always doing so, IBM could use numbered suffixes to indicate any major difference (be it key-switch, keyboard assembly profile or added integrated pointing device) to the original Enhanced or Model M Converged Keyboard designs.

Between Models F and M, ASK has not observed major keyboard families that could have taken the designation "G". There were various singular keyboard designs in the interim such as IBM PCjr's original and revised keyboards, but they were not intended to be flagship products, and to my knowledge, there is no evidence suggesting they had a specific "Keyboard" or "Model" designation. There were also regional-specific keyboard families such as various IBM-Alps keyboards in the Far East and Oceania, but those weren't intended for (major) use in EMEA, North America and South America (the traditional markets for IBM's major keyboard platforms).

Rear labels

Until recently, the most substantial evidence of a "Model G" existing were these rear label stickers found on the base plates of mid-1980s IBM Enhanced Keyboards made in the United Kingdom. It should be noted that to my knowledge, IBM U.K. never printed "Model M" on any of their keyboards, so this in itself is interestingly uncharacteristic for them. Three styles of this sticker are known:

  1. A monochromatic P/N 1386751 one with dot-matrix printed text that explicitly declares "Model G" and all its text is squished towards the label's lefthand side.
  2. A monochromatic P/N 1390343 one with dot-matrix printed text that explicitly declares "Model G" and all its text is wider to fill the entire label.
  3. A blue P/N 1390343 one with smoother printed text, set fields for handwriting, and a large "G" in the top-right corner.

To my knowledge, they were present on keyboards made between 1985 and 1987. I've never seen an IBM InfoWindow Display Station Enhanced Keyboard (which was introduced in 1989) with such a sticker, but those InfoWindow keyboards led me on to something else later...

Lexington Today

Until 19th May 2024, the ASK Wiki's IBM Model M keyboards page previously made reference to "Model G" based on just the evidence above, mentioning the possibility of this being the original designation but without definitively saying as much. On 19th May 2024, deskthority user rocco_16v replied on their Help Dating a Silver Badge Model M thread with a scan given to them by IBM Corporate Archives providing the most concrete evidence of "Keyboard G" (along with a good amount of background information).

See the linked thread for the full scan (copyright of IBM)

The scan is from an internal communications magazine called Lexington Today. The IBM Enhanced Keyboards for IBM 3161 and 3163 ASCII Display Stations (for US English usage, part numbers 1386303 and 1386304 respectively) are the subject. This is interesting as it states the announcement also features "a significant keyboard announcement as well - a new Lexington keyboard" (attention to the keywords "announcement" and "new"), despite the fact a month before this communication was published, IBM had already announced the IBM 7531 and 7532 Industrial Computers that sported their own Enhanced Keyboard variant[8][8]
IBM - IBM 7531 Industrial Computer Brief Description of Announcement, Charges, and Availability [accessed 2024-06-12].
IBM - IBM 7532 Industrial Computer Brief Description of Announcement, Charges, and Availability (#185-054) [accessed 2024-06-12].
. Anyway, Keyboard G was seen as a significant accomplishment by IBM in terms of cost, ease of use (especially regarding layout), and they even expected the keyboard's membrane technology to offer more reliability than the capacitive technologies used by Keyboards B and F[7][7]
IBM - Lexington Today - New IBM Product Features Lexington Keyboard [accessed 2024-05-19]. License/note: accessed via a deskthority post courtesy of rocco_16v & photo excerpts used under fair dealing.

IBM documentation

From here, it's unclear exactly when or why "G" became "M". But with the confirmation that "G" existed as a designation outside of some Scottish-made keyboards, I started reevaluating some things I've come across and not had the initiative to explore before. There are in fact various mentions of "G" in IBM documentation to take a look at.

Until now, the most I (unwittingly) came across was within IBM i documentation. IBM i running on IBM Power Systems is the successor to IBM's earlier midrange computers such as System/34 and AS/400 which both supported IBM 5250 family terminals. IBM i (being their descendant) includes many references to 5250, including twinaxial InfoWindows and their keyboards. The SBCS keyboard and display part numbers by language document is heavily referenced by ASK as its the primary source of keyboard part numbers for twinaxial InfoWindow keyboards, and the column for Enhanced Keyboard part numbers is in fact labelled G keyboard. On its own, it could mean anything, but given there are other references to "Model G" == "Model M", I find this hard to ignore.

The column for their 122-key counterparts is distinguished as "1A keyboards" though. The part numbers in that column are Type 3 122-key Model M Converged Keyboards, which should be within the same overall keyboard family as Enhanced Keyboards (that includes "G" if it's just the original designation for "M" in general). In a similar style as the "G" labels shown before, I have also spotted "1A" internal rear labels. I also noticed that the large rear labels used for IBM Netherlands Type 2 122-key Model M Converged Keyboards have a "model" field stating "K1A", which I assume to mean "Keyboard 1A".

Furthermore, the IBM InfoWindow 3471's 1989 announcement additionally states there is a "1B" as well[13][13]
IBM - IBM InfoWindow 3471 Display Station Brief Description of Announcement, Charges, and Availability (#189-096) [accessed 2024-06-13].
, which looking at the part numbers included - 09F4230 and 09F4231 - are IBM 104-key Quiet Touch Keyboards. Whilst somewhat resembling a Model F or a Model M and bearing the physical layout of the so-called "unsaver", they're not based on either platform and in fact use Micro Switch ST-series rubber dome key-switches. Whatever this nomenclature is, it goes outside the Model M family.

With that in mind, I completed a small literature review of sorts from what I could find in the IBM announcement letter archive, bitsavers' PDFs, and on the Internet archive. I found mentions of "G" and/or "1A" in various IBM 3270/mainframe, 5250/midrange and RT PC related documents.

So whilst in the prior section "G" is being titled as if it's the successor to "F", it seems like after the "M" designation became a thing, it was repurposed to mean just the original discrete keyboard of the family - the IBM Enhanced Keyboard - and it was used alongside some new model designations for IBM Converged Keyboards and things like them.


I pretty much assumed "Model G" was a thing in some shape or form for a while. With early IBM U.K. made Enhanced Keyboards having it printed inside, it was too hard to ignore the possibility. The discovery in May motivated me to dig deeper and find a potential narrowing of what "G" meant. As such, I draw the following conclusions from what I've found:

  1. "G" was likely intended as the original designation for the "F" successor. At some point (probably just) before general availability, the production keyboards became "M" (as seen on the backs of IBM U.S. keyboards) but internal communication and factory labelling weren't fully updated or "G" continued in some form as an internal designation and was perhaps reinterpreted by individuals and teams working on them. Anyway, in the original capacity, it was written as "Keyboard G" and "Model G".
  2. Whilst "M" became the overall designation of the entire Model M keyboard family, "G" was reinterpreted in some capacity to refer to the original discrete Model M design - Enhanced Keyboards - only. This was mostly for IBM 3270 and 5250 terminal family documentation but even for IBM RT PC as well. In such cases, it was also be written as "Type G" or "G keyboard".
  3. After "G" was repurposed to become Enhanced Keyboards, "1A" and "1B" were introduced to refer to various members of the IBM Converged Keyboard family (122-key Model Ms and 104-key not Model M Quiet Touch Keyboards respectively).

ASK content will be updated to mention some of the above in short order. As to why "G" became "M"? I'm not sure about that one. I think it's fairly safe to assume it might stand for "membrane" given the obvious technology difference between Model Ms and Model Bs and Fs. I just wish there was something official to confirm that... I still have other questions regarding "G" left as well. Whilst the above is my best understanding at the time of writing, I of course always endeavour to continue researching when able to and thus not 'calling it a day' on the topic yet and will update when able to.


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

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