Does copper migrate through silver?

What you have is the silver corroding the copper underneath. This causes pock marks on the silver plating which cooks from the voltage applied to it, hence the coloration. Could very well be there's no nickel under the silver (typical of cheap-o plating with brighteners added to the silver to cut it.)

Pierre Spray, Mapleshade guru, says that using refrigirators as cable burners condition the molecules with unmusical properties and you need a zillion hours of music playing to recondition them ! (IF, they are able to be
reconditioned again!) Theo

The ACME is silver plated directly over the 688 brass, no substrate and 200 microns deep.....The brownish color is sulphur from air polluton and not copper leeching through or oxidation as silver doesn't oxidize at room temperatures.......I have some glorious sounding Switchcraft panel mount IEC connectors from fifteen years ago that have turned almost black with the sulphur.....

Crump, I have two oil refinery less than two miles from me!

Should I do something about the air quality in my apt? I've been concerned about that.

So much for Audiogon's lawyer out of place comment...

Psychianimal, I live in Houston so enough said about air quality as I have gotten to the point I don't trust air I can't see :-) Time for us both to move.....