I was cracking open a proof set this morning and discovered that the cent had some sort of corrosion on it.
I'm curious if anyone knows what causes this. I would suspect that either the seal was not good and something got inside or there was something that got sealed inside with the coin. If anyone knows, I'd love to hear.
Quote: Any idea what would cause that in a sealed proof set or does that even matter?
Someone sneezed and a couple droplets settled on it before it got sealed in the holder. On both of the large spots you can see roughly in the center of each the remains of what caused the corrosion spot.