This came from the Enterprise factory and contains a complete DRAM refresh circuit based on 3 NE522 timer chips plus all the decoding glue needed. Insert a 4116 DRAM chip and hit the TEST button, instant pass or fail. Very handy thing to have given the number of machines I have that contain 4116 DRAMs. It came to me with another factory relic, a STAG PP16A ROM duplicator :)