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<p>[QUOTE=&quot;Conder101, post: 168623, member: 66&quot;]I do see what appears to be a couple small spots of corrosion but I do not believe that is what is causeing the color change.&nbsp; And I think we can discard the idea of PVC contamination having eaten through the clad layer.&nbsp; (&quot;PVC residue&quot; by itself is actually harmless.&nbsp; The damage is caused by outgassing from an old PVC holder absorbed by the residue and water vapor from the air that combine to form hydrochloric acid which the residue holds in contact with the coin.&nbsp; If that happens the surface can be etched fairly quickly, but it would probably take a hundred years or more to eat through the clad layer.&nbsp; Unless the acid is constantly replaced, the etching of the outer layer will consume the acid and the reaction will stop.)&nbsp; It looks to me simply like a discoloration of the metal.&nbsp; It doesn&#039;t appear to be a case of a partially missing outer clad layer.&nbsp; This is the best I can say from the images.[/QUOTE]</p><p><br /></p>

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