It’s one of these things. Trying to figure out a no brake light problem. The wiring seems fine but the connectors that link to this circuit board are shot. Never disassembled any other vehicle’s taillights so no idea if a circuit board is unusual or not. I do believe 124s had something similar?
No clue what the OC marking means. 137 AS is for Lancia Beta Monte/Scorpion, the D and S probably stand for destra and sinistra I would imagine.