CGA card (Mitsubishi Electric) with 192K RAM?

Digging through old PCs, on a battery-removal spree... came across a Sperry 3070 XT-a-like (I wouldn't quite call it a clone, it's a bit goofy) which has a Mitsubishi Electric system board, RAM expansion, and video hardware. The video hardware is... odd. It's actually two full-length boards, joined with a large IDC cable along the top edge as well as via the ISA bus. The only "complex" IC is a 6845 - other than that it's masses of TTL. Output is via a DE9, and pinouts seem consistent with CGA (15.7KHz on pin 8, 60Hz on pin 9, 3/4/5 at TTL levels and 1/2 ground). There's also an RCA jack on the backplate, and that 6845 IC... it all seems very CGA-like, except that total video memory is 192KB. CGA was normally 16KB, I believe. Hercules and EGA 64KB, although I think toward the end of EGA's existence there was a 192KB option. Physical outputs aren't consistent with EGA's two bits per pixel, though. Does this ring any bells with anyone? I don't know why it needs such a large amount of RAM if it's stuck with CGA capabilities. One board is branded WECD10 and the other WECD11, but there's no "model" or anything. cheers Jules