Parity or not ?
They aren't PS/2 ?
I haven't found them in
http://ps-2.kev009.com:8081/eprmhtml/eprm/233.htm
A standard (read clone) 486 motherboard doesn't recognize them at all ...
No wonder.
These parts are 4MB modules for the S1.5/S2/S3/S4 RAM cards
used in the first RS/6000s.
Probably they aren't simply parity (x36) but x40.