Cromemco 8K Bytesaver   
The Cromemco Bytesaver could accommodate eight 2708 UV erasable EPORMS. It typically contained the monitor and system boot programs for early Cromemco systems.

What was nice about the card was it had an integral PROM programmer along with a DC to DC power supply to generate the required 12V programming voltage. They supplied the software as well though the typical Cromemco Z80 board monitor software had a burn PROM function with this board. The switch at the top left corner was there to prevent accidental programming.  It was an early Cromemco board so it also came as a kit.
 
The manual for the board can be obtained here.