The Model M keyboard is a designation for a group of computer keyboards manufactured
by IBM, Lexmark, Unicomp and MaxiSwitch, starting in 1984.
The many different variations of the keyboard have their own distinct characteristics, with
the vast majority having a buckling-spring key design and many having fully swappable
keycaps.
Model M keyboards have been praised by computer enthusiasts and heavy typists because of the
tactile and auditory feedback resulting from a keystroke.
The Model M is also regarded as a timeless and durable piece of hardware.
Many units manufactured since the mid-1980s are still in use today, while the computers
and monitors of the day are obsolete.
Unicomp, which now owns the rights to the design, continues to sell Model M keyboards.
Recently, the keyboards have made a comeback among writers and computer technicians.
Unicomp has had difficulty making them profitable because they rarely break, and most retailers
will not stock such an expensive keyboard.
History
The Model M was designed to be a more cost effective keyboard than the Model F keyboards
it replaced.
Production for the original Model M began in 1985, and the keyboards were often bundled
with new IBM computers in the 1980s.
These keyboards were produced by IBM in their plants in Lexington, Greenock and Guadalajara.
The most common Model M variant is the part number 1391401, which was the US English layout
keyboard of the IBM PS/2.
Until 1987, the keyboards featured a detachable AT cable; after that, they were bundled with
a detachable PS/2 cable.
Cables came in both 5- and 10-foot lengths.
From about 1994 onwards, the majority of Model Ms were manufactured with non-detachable cables
to cut down manufacturing costs, as well as the Microsoft Windows keys for the then-upcoming
MS Windows 95 operating system.
On March 27, 1991, IBM divested a number of its hardware manufacturing operations, including
keyboard manufacturing, to the investment firm Clayton & Dubilier, Inc. in a leveraged
buyout to form Lexmark International Group, Inc.
Lexmark continued manufacturing the Model M keyboard in the United States, United Kingdom,
and Mexico with IBM being Lexmark's major customer.
Many of the keyboards had IBM assembly part numbers 52G9658, 52G9700, 82G2383, 42H1292,
and others.
Because of pricing pressures, many of these Model M keyboards were manufactured with a
new lower-cost keyboard design to improve its competitiveness in the keyboard business.
Lighter weight plastic, integrated keyboard cable, and uniform print color on the keys
were some of the changes made.
On March 27, 1996, Lexmark's contract to produce keyboards for IBM expired, and Lexmark transitioned
its keyboard business to IBM and other vendors.
Some of the keyboard manufacturing assets were sold to a group of Lexmark employees,
who formed Unicomp.
The Model M keyboard, similar to part number 42H1292 but first renamed 42H1292U and subsequently
the "Customizer", is still in production.
A variety of configurations are available from Unicomp, including updated 104 and 105-key
layouts, a Linux layout, models with integrated TrackPoint pointing sticks or integrated trackballs,
and POS-specific models, such as those with built-in magstripe readers.
When Lexmark discontinued production in March of 1996, IBM continued production in Greenock,
Scotland and subcontracted production of the Model M13 keyboard to Maxi Switch in Mexico.
Production of Model M keyboards by these companies ended in 1999 and 1998 respectively.
Although current Unicomp models may still be purchased, original production models retain
their value well among collectors as well as computer enthusiasts.
There are numerous variations of the Model M, but many of them are exceedingly rare.
Sometimes it may be problematic to get them to communicate properly with a modern computer.
A PS/2 to USB adapter would be necessary for computers without PS/2 ports, and the AT Model
Ms additionally require an AT to PS/2 adapter.
Some PS/2 to USB adapters are unreliable because the Model M tends to draw more power than
they expect.
Unicomp manufacture USB models as well as PS/2 ones, obviating this issue.
Design
The model people commonly refer to when they mention "Model M" is Part No. 1391401, which
was by far the most common.
This enhanced keyboard model included the patented buckling spring design and swappable
keycaps, as well as the heavy and sturdy design of the Model Ms in general.
This keyboard is widely praised as being well-built.
Evidence of this can be seen in the fact that keyboard design has changed little in the
past twenty years, while the designs of everything from PCs to monitors to mice have changed
dramatically.
The sturdy design of the keyboard allows even the most abused to survive for years.
The various models of the keyboard had small differences, while keeping the style of the
key mechanism that makes the boards unique.
The 1391472 model, for example, does not have a separate number pad, rather it incorporates
a number pad into the body of the main keys as many laptop keyboards do.
Likewise, the early 1390120 series did not feature LED indicators for the locking keys.
The Buckling spring design gives the keyboard a unique feel and sound.
Unlike the common dome switch design, the Model M’s buckling spring design gives users
obvious tactile and aural feedback.
Many users report that they can type faster and more accurately on the Model M than other
keyboards.
In addition, the Model M keyboard is less susceptible to dirt and wear and tear; while
dirt will interfere with proper operation of a dome switch keyboard, the design of a
buckling spring keyboard is such that any dirt that falls between the cracks usually
fails to make it into the spring mechanism.
Failure of the mechanism to operate properly would require a large amount of accumulation,
which is unlikely to occur.
There are some drawbacks to the Model M design.
Because the keyboards are so heavy it is not as portable as many modern keyboards.
The keys are noisy enough to be inappropriate in a location where noise is an issue.
Also, liquids spilled on the keyboard do not drain out, and remain in the keyboard with
potential to cause a short circuit.
The 42H1292 design, the 1993 59G780, and post-1993 1370477s and 1391401s, mostly made by Lexmark
and Unicomp, include drainage channels to prevent this.
Identification
All Model M keyboards manufactured by either IBM or Lexmark feature an ID label on the
underside indicating the assembly part number, individual serial number, and date the keyboard
was manufactured.
There are other more obvious ways to distinguish between the range, namely the type of badge
featured on the top of the keyboard.
The first model Ms featured a square aluminum IBM badge in the top right corner.
Part number 1391401 featured an oval, white IBM logo with grey lettering in the top left
of the board.
The later IBM manufactured keyboards and subsequent Lexmark keyboards of the early 1990s featured
a similar oval badge to part number 1391401, but instead with a grey background and blue
lettering.
Features by part number Note: The manufacture dates are approximate.
Click "Show" to display the uncollapsed table.
Gallery
See also IBM PC keyboard
References
External links PC keyboard, Unicomp – current Model M
manufacturer.
Clicky keyboards – distributor of refurbished and never used Model M keyboards.
Inside the World's Greatest Keyboard, PC World . Care and feeding of an IBM Model M keyboard,
Preater – a Model M restoration guide.
Cramer, Ryan, "The IBM Model-M Keyboard", Timeless Tools, RCD .
Product Review: Unicomp Ultra Classic keyboard, or, the IBM Model M reborn, The Story's Story
– Comprehensive review.