Now I find talking to myself...

Judging by the numbers on small quartz oscillator (4S1431A)

which, I think, is marking for 14.31 MHz and looking at this picture (note the similarities - same Texas Instruments chip, same rotary switch, vertical RAM chips)

http://img269.imageshack.us/img269/8723/quick16lcpdsvidcard.jpg

I think it is some sort of video card, except that the connector might not be original.

EDIT - connector might be original, after all. This Radius SE/30 card uses the same connector:

http://farm5.static.flickr.com/4072/4427695621_baa1f8380b_z.jpg