Printers from military surplus with absolutely no documentation and an obscure interface connector... sounds like a good hacking project.
There's a lot of traces under the chips too.
I'm thinking that if I don't succeed in getting it working. I might strip the board right down, so that you can have an image of the front of the board without having to trash one for yourself.
Here's the back of the board too.
The "big chip"... Possibly a custom chip just for this device. I've not found any details as yet.
The "smaller chips"... Plenty more details on these:
INTERSIL ICL7642ECPD - S8936 - Dual/Quad, Low Power CMOS Operational Amplifiers
MAXIM MAX232CPE - RS-232 --> TTL converter https://en.wikipedia.org/wiki/MAX232
74HC14N - Hex Schmitt-Trigger Inverters
74HC02N - Quad 2-input Positive-NOR gates
LA-180D 46 062028
That Maxim chip looks like a good place to tap in a serial port at either RS232 or TTL voltage.