doesn't seem to have much RAM
For what the machine does, 2K is probably plenty.
I mean, obviously. Whatever it did, it was able to do...
I have no idea what the machine does. Did someone link the manual above and I scanned past it?

The ADC/DAC does suggest some analog data processing, but it could well be low bandwidth process parameters, or even housekeeping like voltages and temperatures. My guess would be it's one or two serial interfaces, perhaps stateful with something like an ANSI command line (terminal) interface, perhaps with some relationship between the two channels (maybe one is master to a PC, the other collects data from more devices; maybe they're equivalent and it's like a multi-user terminal interface; lots of possibilities). The 16550s (versus 8250s or Z80-SIOs) imply modest bandwidth, but obviously nothing a Z80 can't handle. And the small RAM implies not much buffering, enough to run terminal interface(s) say, and some kind of basic state machine for the actual core functionality.
Tim