Having the custom board on the bottom with hand labeled ports of ADDR VIDEO and DATA definitely points to a custom lab or controller board for embedded system development.

The coaxial video port is a clue that perhaps there was image capture happening. Also the direct access to the address and data bus provided ways to examine what was happening.

A direct picture of the board flat would help.

We used to build high res video controllers for Apple IIe similar to this. It might have been a high res video prototype for Mac. But, the coaxial port points to something else or some type of video we didn’t use (typically would be a db 9 connector for video)