If anyone's curious,
here are the pictures.
What's interesting, the label claims:
- 6311 model (which would imply Acer switches and ANSI layout)
- Czech localization (which is correct wrt keycaps, but the case itself has German (!) legends on the LED sticker)
- manufacturing date in '92 (which sounds plausible)
However, it's clearly ISO with clicky white Alps mounted in a metal plate (which would imply 6012 model or something like that).
I'm even more confused about keycaps: they're on the thicker side, but I'm not sure, if they're dye-sublimated PBT… they're on the thicker side, I see hardly any aggressive yellowing/shine and keycap legends are somewhat deceptive (some localized legends are certainly pad-printed, though, unsure if pad-printing and dye sublimation have been combined), but something about them is different from PBT dyesubs from Alps Bigfoot or IBM Model M.
Perhaps some previous owner or even the manufacturer made a frankenboard… or there's incomplete information out there in the wiki etc.