If the fingers on some memory or other board aren't gold...

[zamistro]

then what are they plated with?

I'm seeing it on some RAM that is about 10 years old and these boards that date to the 70s.

 

[g_axelsson]

That is tin plate. For confirmation just rub it against a paper and watch the gray streak.

The boards in itself could be quite valuable as is for vintage computer collectors. Some boards from Digital mini computers could fetch $50-$100 each. Especially if you have any with core memory, it looks like a woven copper fabric with small black rings where the copper wires meets.

/Göran