PVC? Verdigris? schmutz? It's a gold coin...

Stork

I was looking at a half sovereign under magnifications I normally don't use and saw green gunky stuff on it. I'm guessing PVC and if so, does it do much harm to gold? It's in a TPG holder and I'm thinking to send it to them for 'fixing'.

edited to add: there's a bit more on the obverse and some on the reverse too.

7Jaguars

Looks like verd & the type they used to use rose thorns to remove. I would think Jewel Luster might do the trick on that although may remove other patina as well.

Boosibri

I don;t think this is verdigris as since verdigris is formed by oxidation on copper or brass. I would say that this is likely PVC or some other contaminate and I'd remove it with acetone vs. something like Jewel Luster. I have also seen free "gunk" on some gold coins and believe that it comes from storage in leather.

Stork

I was guessing PVC (but the leather storage is an interesting thought). Verdigris occurred to me as there is copper in the alloy.

The coin is in a slab, so I think I'll send it to it's respective grader.

I recently saw something very similar on another coin, but in the competitor's slab...so I'm not pinging on one TPG or the other. Things change over the years and they can only see what is present when the coin is in front of them.

Does PVC cause the same harm to gold? I'm guessing yes...even if it's just to the other metal content.

Boosibri

PVC will not harm gold.

I don't think that the ~10% copper in the allow would cause verdigris to form. When silver oxidizes with copper in the alloy it is called tarnish. Gold generally does't oxidize unless heated or exposed to other contaminants.