Might have found another clue from a different reference number on the PCB (IBM 69X5771)
IBM 69X5771 - L M N P G Card (01A-B1 BD
Found it on a legacy parts supplier site. Anyone know what LMNPG means? Google didn't help much. I emailed the parts supplier, but you know how it is, no dollar transaction, no help.
Sorry to be so tiresome about this subject, but I hate an unsolved mystery!
Cheers
Tim