How Did This Happen To These 1981 Proof Coins?

After looking over some hundred + ways a coin could be altered in the minting / packaging process, I've found that the mint has been known to experiment with anti-tarnishing agents to help preserve the coin's luster, many of which had failed.
But it seems that the mint keeps it's methods pretty well hidden from public view, so I guess there's no real way to find out?

If I could just find some coins with similar effects caused by improper storage, I'd be happy. It's kind of my nature to obsess about things until I found out the truth, otherwise.

Lots of factors cause toning. Humidity is one factor. Another is what the set was stored in proximity to. Sulfur is a common culprit that causes toning. I remember hearing that some collectors sealed coins in a plastic bag with a book of matches to try to obtain desirable toning. Some people feel that these coins are worth a premium with toning:

https://www.ebay.com/i/283791114449...As_zEALw_wcB





LOL. We'd call that one TNTC where I work.

IMHO, PSD from moisture (and sunlight?) creating an impaired proof set.
The bumpy surface definitely looks similar to moisture/humidity damaged coins. Coins pulled out of wet ground conditions will have this bumpy texture.

I wouldn't be surprised if it was the effect of extreme temperature changes causing moisture to condensate on the surface of the coins. The fact that all coins seem to be affected seems to rule out an individual process at the mint (Experimental "washes" and such) since each metal composition would be treated differently.

The spots on the SBA was probably where the water collected around dust particles.