What's on this coin?

Cladiator

I'm talking about the dark spots all over the reverse and obverse. Corrosion? PVC?

kamehameha00

It could be tape residue.

poorguy

It doesn't look like it's pitting into the coin from what I can tell from the scan. Is it? If it is pitted then it's probably corrosion or environmental damage.

Cladiator

I don't own the coin, the pic is from an ebay auction. You're right though it does not look to be pitted.

LUCKOFTHEIRISH

Could be carbon spots. Sometimes, this causes a strike through.

wam98

I have seen this before on a seated quarter. It looked like corrosion eating at the surface. My guess, some kind of salt and moisture.

earlwbollinger

I have a 1858 penny with larger black splotches and smaller ones too.
The splotches look like they are right on the surface only, like paint maybe.
I tried a number of things on the splotches. Oilve Oil, Acetone, Trichlor, and Goo-Off.
The best you can do is get some of them to reduce in size.
otherwise the black splotches are permanent and extend down into the coin itself.

I think that some moisture droplets get onto the coin's surface, then a sulfur like polluted environment causes
the black to appear (like sulfuric acid forms from the moisture). Maybe condensation if the coins were sealed up someplace.