Well, one can only hope that, over time, enough people make the effort to add their keyboards to the Deskthority wiki (or similar — not sure how far off the Keyboard Database is) such that it will be possible to look up most "notable" keyboards in existence and get basic details. I'll let you calculate the odds on that happening.
I'll also let you ponder on what a "notable" keyboard would be. With a database-driven site, it should be fairly easy for everyone to simply post every single keyboard they have access to, good and bad.
My wild guess for the Compaq is either NMB Hi-Tek linear (corner LEDs definitely supported) or Key Tronic foam and foil (don't know if corner LEDs are actually supported with those), but it could be anything, and I have no idea. The LED positions rule out Alps, and imply not Cherry either (not unless it's pre-MX). Someone recently found a Scandinavian microcomputer keyboard that turned out to have Honeywell Hall Effect, so you can have some real surprises.