From that time frame, I'm guessing DB-9, like my Panasonic 19" 2-bit Card.

It hardly paid to find a lower pin count connector than that, 3 & 4 BNC Cable minimum configs requiring 6 and 8 pins along with the shroud for proper grounding and all. Economies of scale had a lot to do with backplane connector choices in that era. Which makes apple's choices more than a tad odd. Was the AAUI port connector used for anything but 10baseT , on Macs, or out in the real world?