The IBM Model M keyboard went through 3 revisions.
- The original keyboard was made in 1987. It is the de facto standard for modern keyboards today, minus the Windows keys. Featured a full length spacebar, tactile response feedback, a detachable cord, and no unnecessary keys. This keyboard was a marvel of engineering.
- The second revision, made around 1992, took the original Model M design and added drain holes for liquid spills on the back of the keyboard, and side walls so the keyboard was inset into the frame itself -- acting as a sort of gutter for liquid spills. They also took the original grey logo and made it the IBM blue logo that we know today.
- And then, the third revision, made circa 1995. For reasons unknown, IBM sold off their keyboarding division to Lexmark, who then proceeded to butcher the design. This revision features a cord embedded into the keyboard, no clickey keys, and a general feeling of integrated cheapness. This is the end of the original Model M era.
These keyboards truly are indestructable. Some time ago, I was at an anti-smoking assembly, and there was a part where they smashed old computers up to prove what a waste of money smoking is. They invited students to come up onstage and smash old IBM computers with a sledgehammer. The IBM PS/2 case split open like soft cheese when hit, and so did IBM's CGA monitors. However, when one student tried to smash a Model M keyboard, I couldn't believe what was happening before my eyes.
The keyboard would not break apart after repeated blows with the sledgehammer
Keys went flying everywhere, but the keyboard remained intact. The student gave up and smashed another PS/2 computer.
On June 10, 2002, my IBM Model M keyboard (tattooed 626-5569 by my local high school's surplus department) will turn 10 years old -- even after 10 of very heavy use. it works just fine.
More info can be found at www.modelm.org, where I learned about these revisions.