Late-model Hercules card

I've got a full-length ISA (although the last 4" or so is bare PCB, not even any ground plane) Hercules card here which seems to have been built in 1990. On board we have lots of TTL glue, a pair of 50464 RAM chips, a 24 pin "Hercules font ROM", a 6845, and a 40 pin HG61H15R81P IC. Card edge just has a female DE9 connector. Oh, FCC ID is "EW65T5HERCULESTAN". No obvious model number. 1990 seems quite recent, given that we were into SVGA territory by then; sure there were some CAD applications which would make use of an additional video board, but the market must have been small. Based on the above (and to save me having to trace pins) can anyone confirm that the board is compatible with the original Hercules card and will hook up to an MDA display? Given the date I just want to check that it's not one of their CGA or EGA compatibles. cheers Jules