I think it needs further investigation. I forgot to mention - i also tried 'brasso' a product for reconditioning tarnished brass. I figure what helps one metal may possibly help another. But - yeah - i guess (it appears and makes sense) that this is an organic compound (my guess is related to and deposited by, the rubber pills).
There is a very definite directional 'grain' to this yellow contact metal (without trying to argue that it's copper or gold) - so it's either been 'worked' before - or it's simply the result of the machining of the metal (in this case would have to be copper - since gold plating would smooth out this machining pattern). With the steel wool I rubbed through the resist on one of the traces adjacent to the pad by mistake - revealing the exact same colour of metal. So either the whole board was gold plated and THEN the resist sprayed over top - or else the pads are just copper (but then after so many years i would expect to see more oxidation if that were the case) - the jury is out on this.
I just wanted to add my additonal thoughts from what i found. I will compare the grain structure to my other polysix key contacts.
There is a very definite directional 'grain' to this yellow contact metal (without trying to argue that it's copper or gold) - so it's either been 'worked' before - or it's simply the result of the machining of the metal (in this case would have to be copper - since gold plating would smooth out this machining pattern). With the steel wool I rubbed through the resist on one of the traces adjacent to the pad by mistake - revealing the exact same colour of metal. So either the whole board was gold plated and THEN the resist sprayed over top - or else the pads are just copper (but then after so many years i would expect to see more oxidation if that were the case) - the jury is out on this.
I just wanted to add my additonal thoughts from what i found. I will compare the grain structure to my other polysix key contacts.