The board  was a Programmable  Read Only Memory   (PROM)   card,   capable of providing up to 2K bytes of PROM memory using either the  1702 or 1702A type PROMs   (8 bits by 256 bytes per PROM). The card is  designed with provisions  for switching the Vcc power supply  to reduce unnecessary power consumption.  The card could  be set for 0  to  3 wait states  to accommodate different PROM speed devices.
 
The manual for this board can be obtained here.  It is one of the few S100 manuals that has memory/port  locations in octal. Clearly a very early S100 bus board!