Fred Mau
   15-pin *male* connector on the PC board ? Almost has to be a 5250 Display Station Emulation Adapter (DSEA), It's the only cards Ive ever heard of that uses a 15-pin male. It allows a PC to act as a terminal on an AS/400 twinaxial network. There should also be a pigtail about 12" long with a twinaxial T connector on one end and 15-pin female on the other end that attaches to this card.
   My HMM shows the (early, for system 36/38)5250 DSEA as being a 69X6294 or the (later, for AS/400) 5250 DSEA as being a 64G3506, but maybe there were some variants.

U1 7378945ESD
U3 93X2670ESD
U4 Intel N8259A
U5 Siemens SAB 8088-2-P
A KM44C256BJ-10
B KM44C256BJ-10
C KM44C256BJ-10
Y1 24.0000MHz

The port is a male DB-15 (not HDD15!) The card is marked 93X2695  and another sticker says "To replace card order PN 69X6294"