“Toning” on gold proofs
I’ve had this $5 gold proof for many years, it’s in the original mint packaging. Both the obverse and reverse have some kind of hazy looking crud on them. This wasn’t there when I got it, the entire coin was absolutely perfect. It’s been awhile since I’ve looked at it, maybe a year or so and now I see this…..stuff happening.
Is this coin doomed? I assume the little plastic slabs are sealed at the mint?
What, if anything can I do about it? At the very least is there anything I can do to stop it from getting worse?