Editing IBM Enhanced Keyboard (section)

==Design details==

The Enhanced Keyboard consists of a Model M assembly mounted inside a plastic (usually [[ABS]], or a mixture of [[Keycap material#Polycarbonate|PC]] and ABS) casing. The casing consists of a separate upper and lower part, which clasp together at the front of the keyboard with interlocking tabs, and are secured at the back with four 5.5 mm (7/32") hexagonal screws. The controller card is located either under the keyboard assembly or mounted on the assembly itself, above the numeric keypad. On original examples, the cable exits the casing at the center back of the keyboard; on later ones, it exits at the top right. Older style cases have a square gap in the case which allows for either an SDL socket for a removable cable, or a non-removable cable with a square filler. On variants for the PC/XT and terminals, the lock light area above the numeric keypad is blank. The keys on most Enhanced Keyboards consist of a separate base (stem) and a detachable printed cover, but some used single-piece key. Double-piece key eventually became optional, as some customers found the single-piece design less likely to be lost or stolen. Virtually all Enhanced Keyboards have a small speaker grille on their bottom surfaces; however, only a few variants actually include a speaker (the keyboards of the RS/6000 workstations being the primary example). 

===Distinctive sound===

The Model M's buckling-spring key mechanism has a distinctive sound described as "clicky". Most users accepted the sound as an inherent part of using the keyboards. Some users, including present-day enthusiasts, consider it a reminder of the Model M's sturdiness compared to other manufacturers' quieter but cheaper and less durable rubber-dome keyboards (many of which were made to resemble the Model M).

Some customers requested quieter keyboards for situations requiring them (e.g. libraries and medical facilities). IBM responded by producing Quiet Touch Keyboards with rubber dome switches instead of buckling springs, and with a different style of key stem. While not as prized today as buckling-spring Model M's, many Quiet Touch Keyboards are still in service and are considered among the best rubber dome keyboards made. A later initiative to provide a quieter Model M, without conceding to rubber domes, was the [[#8184692|Soft Touch Keyboard]] made by Lexmark for IBM from 1995–96, whose buckling springs were greased to reduce their volume.

===International Enhanced Keyboards===

In contrast to IBM's previous keyboards, the Enhanced Keyboard was produced with two different physical key arrangements: one for US English and another for Europe, the Middle East and Africa. (Far Eastern IBM keyboards, with unique designs, were manufactured by IBM Japan.) This likely mirrored tastes in typewriter layouts: Non-U.S. keyboards often included dedicated keys for accented characters in other languages; the US market preferred large shift and return keys, considered easier for typing. For the international market, IBM had a 102-key layout (later known as the ISO layout) seemingly inspired by the 5251's key layout. These keyboards were produced in IBM's plant in Greenock, Scotland (where they also made PCs, terminals and laptops for the non-US/non-Japanese markets). The standard Enhanced Keyboard had the necessary membrane contacts to support both ANSI and ISO layouts, so the only physical difference aside from the different keycaps was the location of the spring/hammer assemblies to accommodate the appropriate keys.

Unlike in the US, the Greenock plant remained under IBM's control after the Lexmark divestiture. IBM continued to manufacture ISO layout Model M's, but followed the trend of Lexmark's keyboards and adopted the 'blue' logo and drainage holes. Unlike their American keyboards, IBM changed these designs without changing their part numbers, meaning that for each ISO part number there are three distinct variations. Around 1994 they switched from a 1391401-based design to a 52G9xxx-based one. By 1995 or 1996, they had changed to a 42H1292-style design. Due to more stringent regulations in the EU/UK compared to the US, many Greenock-made Model M's also have electrically-grounded space bars made out of ABS (often easily recognisable by yellowing) to prevent static electricity (often caused by monitors, then based on cathode ray tube technology) from building up and discharging into the user. Furthermore, Greenock-made M's with drainages holes do not have drainage channels inside.

In addition to the usual 13914xx part numbers, IBM also manufactured keyboards under a wide variety of seemingly random part numbers. They also made some rubber-dome variants, most of whose part numbers begin with 71G.

US-layout keyboards were also made in Greenock. All 42H1292s made after 1996 were produced there. Earlier variants were also produced in Greenock, sometimes with the same part number, but there were some Greenock-specific US keyboards; for example, the 1396790 was a standard 101-key variant based either on the 1391401 or 52G9658, depending on its year of manufacture. The different part number seems to have indicated a US layout keyboard for customers in Europe, the Middle East and Africa (EMEA). The 1396790 is common in the Netherlands and other countries in the EMEA regions where the US layout is popular. The 1394950 was an Industrial model made from 1996 on, and was largely identical to the earlier 1394946 with one distinguishing feature: instead of the hard plastic label with raised silvered letters, it has a simple flat sticker.

Starting in 1986, IBM also made keyboards at their Mexican PC manufacturing center in Guadalajara, Mexico. These keyboards were largely intended for the Latin American market, although there were also some for the French Canadian and US markets. Lexmark eventually took control of keyboard production there, producing a number of Mexican-made Lexmark Model M's. Production in Guadalajara likely ceased in 1996 when Lexmark stopped making keyboards. Unlike Greenock Model M's, Mexico-made Model M's have no defining characteristics from IBM US/Lexmark Model M's. Mexico-made Model M's should not be confused with the Maxi Switch–made IBM Model M13 derivatives made in a different plant in a different part of the country.

As with US Model M's, international layout Model M's left production in 1999. For most Model M sub-variants (with the main exception of the M15) there were ISO versions, although they are generally rarer.

<gallery widths=250 heights=187>
File:IBM Model M -- spacebar earthing.jpg|Earthed (grounded) space bar from a 1996 Greenock Model M
File:IBM Model M -- spacebar earthing connector.jpg|Earthing connector for the space bar
</gallery>

===Keycaps===
<gallery widths=250 heights=187>
File:IBM Model M -- one-piece keycap.jpg|One-piece keycap ([[caps lock]] from 1996 blue label)
File:IBM Model M -- two-piece keycap.jpg|Two-piece keycap (from 1996 blue label)
File:IBM Model M -- two-piece keycap mount, front.jpg|Front view of same. The two-piece design allowed keycap legends to be easily rearranged (e.g. for alternate key layouts) and reduced the cost of keyboards with custom legends.
File:IBM Model M - stabilisers.jpg|Sliders (with keycaps removed) and stabilisers from 1996 blue label
File:IBM Model M -- 1996 keycap mould defects.jpg|Mould defects in a 1996 blue label keycap
</gallery>