This is a coin I picked up a long time ago. I know it's in really bad shape, but I got it cheap & it's from the area my Grandmother's family emigrated from. Anyway, is the green stuff on it PVC damage or some type of corrosion? Should I do anything about it? I assume the other stuff on it is rust? Here is what I have on it... Pomerania, City of Greifswald, AR Gross Pfennig, Struck: 1424-1425 (ref - Jesse 493, S. 4957)
From the coloration of the pictures, I assume we're talking about silver. If so, PVC is the most logical suspect. If the coin is copper or one of its alloys (brass, bronze, etc.), verdigris would be the main suspect. For PVC the accepted treatment is a dip in pure acetone (not nail polish remover with fragrences and other additives), followed by a quick rinse in distilled or deionized water, and air drying on a soft cloth. Far and away the best method for removing verdigris from your collection is disposing of the coin. Both PVC residue and verdigris can cause pitting of the surface, such as what appears where the arrow is pointing:
Perhaps, yes perhaps a griffin I just finished watching "Harry Potter & the Goblet of Fire" hence the dragon came to mind first. B
How can you be so sure that the metallic oxidation products on the surface of this old coin are from PVC corrosion? I would not worry about it. That coin is undoubtedly made from a crude alloy that contains silver, but what else? Right now, you don't know. Nobody knows. I'll bet it has traces of several metals; Ag, Cu, Zn, Pb. etc.
I'm actually fine with it the way it is, but Roy mentioned the PVC stuff causing pitting. I'm fine with it the way it is, but don't want it to get worse.
