This board has a z80, a bit of memory, 2 Zilog 8420 Parallel I/O chips and a Counter Timer, Z80 CTC I/O chip. 40 pin connector off the edge to some sort of device.
AM9016EPC chips make up 16K of ram
DEC 19-13040-00 DC005 Transceiver logic chips are at U5,7,8,9, and 10
ECO applied to one of the Transceiver logic chips (U10) (pin 15) Appears to go to one of the switch U7 positions.
DEC 19-12730-00 DC003 Interrupt logic chip is at U3
Dec Chip reference is here on Bitsavers CHIPKIT
Below are pictures of the overall board front and back, then various features