Can someone with a GS-Ram Rev A

[Steven Hirsch <snhirsch@gmail.com>]

please tell me what chip is at the far right of the board above the 74LS245? 
I have one with an empty socket at that location.

There have been a number of board revisions, but this is a Rev. A dated 1986. 
It has (5) chips at the right plus two yellow termination resistor packs.  I 
found some pictures on line, but none are clear enough to make out the label 
on that part.  All I know is that it's a 20-pin 0.3" DIP package and I'm 
hoping it wasn't a PAL.

Steve