What are the build dates on some of the ICs on the card? I'm guessing from the context of the period that it may have been mfr'd the 34th week of 1990, which would be about right for a 9 pin D shell connector VidCard.

You're on the right track with SlotInfo and TechTool, so that's strange. Those read the Card Id off the DeclROM. Is there a ROM (DeclarationROM) on the card? If it wasn't designed by Apple's guidelines and relied entirely upon drivers/inits/whatnots to kick start it . . .

. . . you're way up the wrong creek w/o a propulsion device! :

I've got a NuBus card like that, it doesn't show up under any SlotSnoopers readout either..