Digging through a box of SBus cards pulled out of storage, I found a
card marked "© 1991 VIGRA, INC. VS-10 REV B". It's got a back panel
with four switches and a DA-15 connector.
Poking at it with the console FORTH in an SS20 made it look like a
framebuffer. So I de-tokenized the FCode and, sure enough, it is.
I've got it working enough that I could probably build an X ddx layer
for it.