Not sure if this helps, but Sandy references this patent on his page on the Teradrive board:
http://www.google.com/patents/US5010219
The Sega HTR-2106 - Sega + IBM + Alps
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Daniel Beardsmore
- Location: Hertfordshire, England
- Main keyboard: Filco Majestouch 1 (home)/Poker II backlit (work)
- Main mouse: MS IMO 1.1
- Favorite switch: Probably not whatever I wrote here
- DT Pro Member: -
- Contact:
That's the one already cited on the wiki. Mine is an additional one that I came across by accident, and it depicts a different internal design.