Model M keyboard
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Predecessor | Model F keyboard |
| Founded | 1985 |
| Founder | IBM |
| Fate | Production discontinued by IBM in 1996; manufacturing continued by Lexmark, Maxi Switch, and Unicomp |
| Headquarters | United States |
Area served | Worldwide |
| Products | Computer keyboards (buckling spring mechanism) |
| Parent | IBM (original), Lexmark International, Maxi Switch, Unicomp (later manufacturers) |
Model M keyboards represent a line of computer keyboards initially developed and produced by IBM beginning in 1985, with later manufacturing handled by Lexmark International, Maxi Switch, and Unicomp. The majority of these models utilize a distinctive buckling-spring key switch mechanism, possess a consistent key profile, and include interchangeable keycaps. Their reputation for longevity, reliable typing experience, and pronounced tactile and auditory feedback has earned them favor among both corporate users and keyboard enthusiasts.
The widespread popularity of the IBM PC played a significant role in cementing the Model M’s design influence; its ergonomic layout and key arrangement set a precedent for nearly all subsequent mainstream keyboards. This configuration was officially standardized by ISO in 1994 and ANSI in 1998, incorporating enhancements such as the Windows key and Menu key.
Celebrated as a classic example of enduring hardware, numerous Model M keyboards remain operational today due to their sturdy build quality and compatibility with modern systems through PS/2-to-USB adapters. The ANSI 101-key and ISO 102-key layouts continue to fulfill business requirements despite ongoing technological evolution.
During the production periods under IBM and Lexmark, shipments exceeded 10 million units. However, the Model M’s dominance in the general market declined throughout the 1990s as manufacturers shifted toward more economical rubber dome keyboards. IBM discontinued Model M production in 1996.
History
The Model M keyboard was engineered to reduce manufacturing expenses compared to its predecessor, the Model F keyboard. Created at IBM between 1983 and 1984, its design integrated comprehensive user input, ergonomic research, and features inspired by rival products. Its key arrangement—especially the inverted-T arrow keys—drew influence from the LK-201 keyboard associated with the VT220 terminal.
Manufacturing commenced in 1985, with Model Ms frequently packaged alongside IBM computer systems. Initially paired with the 3161 terminal, it was also deployed across various IBM product lines including the 5250 terminal and RS/6000. Production facilities were located in IBM plants situated in Lexington, Kentucky, Greenock, Scotland, and Guadalajara, Mexico. The most prevalent model—the IBM Enhanced Keyboard (part number 1391401)—featured a U.S. English layout bundled with the IBM Personal System/2. Up until approximately 1993, most units included a detachable coiled cable with AT or PS/2 connectors. Starting in 1994, flat non-detachable cables were introduced to reduce expenses; IBM maintained the 101-key format without incorporating Windows keys, which Unicomp later added in their 104-key Model M variants.
On March 27, 1991, IBM divested its hardware manufacturing division—including keyboard production—forming Lexmark International. Lexmark continued producing Model Ms across factories in the United States, United Kingdom, and Mexico, with IBM remaining a principal customer. Keyboards identified by IBM part numbers such as 52G9658 and 42H1292 were bundled with IBM PS/ValuePoint and PC Series machines.
Facing cost reduction pressures, Lexmark implemented incremental design modifications over four years: lightening cases and metal backplates, substituting detachable cables for fixed ones, and adopting single-color key legends. In 1995, Lexmark introduced a significant redesign by relocating the internal controller board to a "press-fit" style that lowered production costs but compromised reliability due to a fragile card-edge connector. This change signaled the conclusion of the classic Model M era; some earlier models remained in production until 1999. Today, only a limited number of press-fit models are still operational.
During Lexmark’s manufacturing period, certain Model Ms employed rubber-dome switches rather than buckling springs; these versions exhibited reduced durability and are less prized by collectors.
A five-year contract obligating IBM to source most keyboards from Lexmark expired on March 27, 1996. Subsequently, Lexmark ceased keyboard production and sold assets back to IBM as well as Maxi Switch. IBM continued manufacturing buckling-spring Model Ms in Scotland until 1999. Maxi Switch acquired rights for rubber-dome keyboards and produced the Enhanced Keyboard with TrackPoint II (model M13) in Mexico until 1998.
Some assets formerly owned by Lexmark were acquired by ex-employees who established Unicomp, producing models closely resembling part number 42H1292 (renamed Customizer) along with other configurations including updated layouts (104- and 105-key), Unix-specific layouts, integrated pointing devices, and POS-oriented models featuring magnetic stripe readers—all utilizing the press-fit controller design.
Unicomp depended on original IBM tooling that gradually degraded over time, resulting in declines in product quality and USB controller issues that maintained demand for vintage Model Ms. In 2020, Unicomp refreshed its tooling and introduced the "New Model M," which offers enhanced build quality reminiscent of the classic 1391401 model while incorporating modern USB connectivity and updated layouts. Some older models have since been phased out or marked as deprecated on Unicomp’s website.
Variations
The Model M was produced in a wide array of versions, often referred to as "part numbers," which differed in color schemes and functionalities. Among these, the Space Saving Keyboard stands out by incorporating the numeric keypad within the main keyboard area, greatly narrowing its overall width and serving as an early influence for the "Tenkeyless" design.
IBM supplied both conventional and Space Saving Model Ms in a gray/pebble finish tailored for industrial applications, intended to conceal signs of wear common in manufacturing settings. Additional industrial features included grounded spacebars and, on certain later editions, drainage holes designed to mitigate damage from liquid spills.
The M2 model emerged late in the Lexmark era as a response to cost competition from rubber-dome keyboards. It featured a slimmer chassis that omitted the metal backplate. Some M2 units employed rubber-dome switches, while others maintained the traditional buckling spring mechanism. The M2 is identifiable by its flat front profile and an "M2" label, differentiating it from classic Model Ms. Due to inferior construction and reliability issues, the M2 is rarely prized by collectors.
Separate from the M2 are the M5 and M13 variants: the M5 integrates a built-in trackball, whereas the M13 incorporates a pointing stick. Both models preserve the durable build quality characteristic of Model Ms and continue to be manufactured by Unicomp under the names Trackball Classic and Endura Pro, respectively.
Design
The most iconic version of the Model M is Part Number 1391401, commonly called the Enhanced Keyboard, which showcases IBM’s patented buckling spring technology along with removable keycaps.
Celebrated for its longevity, many Model Ms remain operational after more than 40 years due to their steel backplates and sturdy plastic frames. The buckling spring switch provides tactile and audible feedback that differs markedly from rubber dome keyboards, often improving typing speed and precision. Enthusiasts also commend its ergonomic advantages in minimizing repetitive strain injuries.
Early Model Ms usually featured a 1.25-inch circular slotted speaker grille on their undersides; however, actual speakers were infrequently installed. Models commonly equipped with speakers include part numbers 1394540 and 51G872, designed for RS/6000 UNIX workstations.
Model Ms were manufactured with various interface types: initial models used PC XT and AT connectors; later ones adopted PS/2 ports, including the 1391401 Enhanced Keyboard. Unicomp eventually introduced USB connectivity. Older versions had detachable SDL cables whereas subsequent Lexmark and Unicomp models employed fixed cables.
Features by part number
Layout categories:
- 84 – Tenkeyless variant based on the 101-key ANSI layout.
- 87 – Tenkeyless version derived from the 104-key ANSI layout.
- 101 – The original ANSI layout of the Model M.
- 102 – International layout featuring an extra key between Z and a half-sized left Shift key; AltGr replaces right Alt; typically includes an ISO-style elongated Enter key.
- 103 – ANSI layout with one Super key and one Menu key; long spacebar.
- 104 – ANSI layout plus two Windows keys and one Menu key; short spacebar.
- 122 – IBM terminal keyboard layout with additional function keys and a function pad on the left side.
Logo placement abbreviations:
- LC – Left Corner
- RC – Right Corner
- LLC – Lower Left Corner
- LRC – Lower Right Corner
- ULC – Upper Left Corner
- URC – Upper Right Corner
- LLP – Lock-Light Panel
| Part number | Switch type | Layout | Detachable keycaps | Detachable cable | Interface | Drainage channels | Logo type, position | Manufacturer | Production years | Copyright | Notable features |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 5152 | Buckling spring | 101/102? | Yes | Yes | DIN-5 | No | Square metal badge, black on silver background, URC | IBM UK | 1985–? | 1985 IBM Corp. | Early UK-produced German Model M variant; labeled "Model No. 1562" and "Auxiliary Power to 5151"; vertical grey tag; thick glossy black cable. |
| A218331 | Possibly buckling spring | 122 | Possibly yes | No | DIN-5 | Yes | Decision Data logo at URC | Unicomp | ?–1997–? | None specified | Standard Unicomp-produced 122-key Model M; features Decision Data's red "ALICE" logo on numpad's upper-right key. |
| ACP0412 | Rubber dome switches | 101 | Yes | No | PS/2 | Yes | "AFFIRMATIVE" logo at URC LLP | Unicomp | ?–2000–2008–? | None; Made in USA | 101-key Model M branded as "AFFIRMATIVE"; dual legends including "Field Exit" on Enter key. |
| 02K3672 | Buckling spring switches | 101 | Yes | Yes | PS/2 | Yes | Blue oval logo at ULC | Unicomp | ?–1998–? | None ("Mfg by Unicomp Inc for IBM") | Industrial dark gray finish with speaker grille; two-tone legends on Alt and Numpad keys. |
| 06H3048 | Possibly buckling spring | 101 | Possibly no | No | PS/2 | Yes | "Multiview Workstation" branding at ULC | Lexmark | ?–1994–? | Lexmark International Inc., 1984 | Standard ANSI Model M featuring extra symbols above function keys; may be a factory variant or overlay. |
| 06H4173 | Buckling spring | Approximately 101? | No | No | PS/2 | Yes | Silver on black oval (Maxi Switch), Blue on white oval (Unicomp), ULC | Maxi Switch, Unicomp | 1997–1999 | Unicomp, Inc. 1984 or none (Maxi Switch) | Industrial dark gray PS/2 model with trackpoint; dual connectors for keyboard and mouse. |
| 0985705 | Buckling spring | 122 | No | No | DIN-5 for IBM 5250 Terminal | No | Square metal badge, black on silver background, URC | IBM UK | 1985–? | IBM Corporation, 1985 | Terminal keyboard with English and Arabic legends for IBM 5250 systems. |
| UB40416 | Buckling spring | 101 | Yes | No | PS/2 | Yes | Unicomp logo located on LLP | Unicomp | ?–Present | Unicomp, Inc. 1984 | Classic black Model M with standard 101-key configuration featuring light gray keycaps. |
| UB4044A | Buckling spring | 104 | Yes | No | USB | Yes | Unicomp logo located on LLP | Unicomp | ?–Present | Unicomp, Inc. 1984 | Contemporary Ultra Classic compact case in beige with traditional light/dark beige keys. |
| UT40U4A | Buckling spring | 104 | No | No | USB | No | Unicomp logo located on LLP | Unicomp | 2020–Present | None; Made in USA | New generation Model M featuring updated tooling; available in black casing with white or gray key options. |
Note: Production dates are approximate estimates.
See also
External links
- – in-depth history and different versions
- – issues with compatibility on modern devices
- – current producer of Model M keyboards
- – supplier of both refurbished and new Model M keyboards
- – guide to restoring Model M keyboards
- – detailed evaluation