Wiltron 6600A series sweep generator - late(?) version CPU daughterboard/1 EPROM

[wb0gaz]

Digging into a Wiltron 6653A sweep generator today, discovered the CPU/EPROM/RAM board (behind the front panel) has a plug-in daugherboard (plugs in where the 8085 CPU would normally go) with a CPU (8085), an address latch, and a single 28-pin EPROM (part number TBD, covered by label.) None of the service manuals I've surveyed document this module (otherwise, the sweepers have five 24-pin EPROMs on a board behind the front panel,a long with CPU and RAM.)

The daughterboard has part number 6600A-D-34053 REV A.

Attached is a photo of the daughterboard.

If you recognize this version of the Wiltron 6600A series sweep generator, would you let me know?

Thanks very  much,

Dave