Lousy scan, and it's still dirty from sitting in the Sun (automobile engine) Diagnostic Computer for 28 years...but it's apparently a rather rare piece.
There's also a memory board, made by Sun, that has four Intel C8316A chips, and four 93448-PC chips that appear to be ROMs, as they have labels stuck on them with neat things like F1L, E0R, E1R, etc. as well as some 74365s and some 7404s and such TTL.
I have to do some more investigating of the power busses, there are some screw terminals on the motherboard which had a bunch of fat wires going to them from the huge power supply...but there's also a screw terminal board on the motherboard, which is marked for voltages, such as +5, -5, -10, -12, and some others that are not so obvious.
And the cpu and memory board slots in the motherboard are not wired the same as the rest of the slots (which hold interface cards mostly)...what fun!
Eric has kindly typed out the edge connector pinout for the IMP-16C.
I found a press release for the IMP-16L in a magazine.