Home made Breadboard job with a Quad NAND gate & NOR gate, and a Dual flip-flop. Perhaps a pass-thru board for diagnostics since it has that LED on it, only nothing uses that size connector in firepower, correct? Is it all 1.56 spaced connectors? I've never owned or worked on a sys6. It would depend on what was sent to it and how the logic state would change. If you take pics of the bottom of the board, I could make a schematic then put it into a circuit simulator, that would make it easier to guess its function.
It could have also been a replacement board made for some sort of IC that was expensive to the time period, since it was 82. Logic was and still is cheaper than most other ICs. The LED could very well just be a power indicator. If it is wired to one of the logic ICs, then it isn't.
Regardless, this isn't a factory thing.