Are you sure these were made by Fujitsu?
The case shape with the wide front lip, key-integrated status indicators and ferrite on the cable are a dead giveaway. Here's a
FKB4700 for comparison. This one has a P/N of N860-4700-T601, so the middle number seems to specify the model. Fujitsu Peerless. The Escom board looks a little different but still very close overall. Sure it's a rubber dome and not a Peerless mechanism (with spring on top, which should be plainly audible)?
You gotta admit, as big and funky-looking these boards are, they do have some style. (Might be a nice eyecatcher at a LAN party.
) Did you pull a key some time? I wonder what kind of lettering these things use. I suspect two-shot molding but that should be visible underneath.