How is it that a professionally graded/slabbed coin can tone? Is the slab not air tight or do other elements come to play? I also have numerous capsuled government issued coins stored in same location where a few have toned and others have not. Thoughts...
I have both PCGS and NGC modern silver coins that have issues. My home is always controlled with lower humidity.
Almost nothing is air tight. Certainly not a chunk of plastic that entombs a coin. I think the biggest thing you have to figure are: what factors were already in play on the surface of the coin before it was put in plastic.
Many are unc/proof silver eagles with hazing, toning or spots. Many of my reverse proofs from 2006 have gone bad
I think it's a combination of ambient storage environment, the metal composition and surface conditions, and the inside of the slab. If many of your slabbed coins are toning badly, then it could be something in the storage environment. But sometimes, it's just something with the coin and/or slab. I have this one (below) as part of a 4-coin set. All the other 3 are still perfect, whereas this one has a milk spot near the horse's tail. Fortunately it's not glaringly apparent (I just took this photo from the worst possible angle to highlight the spot) and, since I noticed it about 2 years ago, it hasn't gotten any worse.
If it happens consistently with someone’s coins it’s something in their environment. Nothing in coins is actually air tight in the sense of the environment could never have an impact and the cost of making something would be astronomical and you wouldn’t be able to see the coin anymore. Something in the coins minting or life before being slabbed could be the cause sometimes as well. That said slabs are by far the best protection
Slabs aren’t air tight. Before I learned my lesson on storage, I had a beautiful type 1 SLQ in my gun safe. It went black on me over the course of two years.
No sir.... A good man here on the board helped me to unload that coin. And I was glad to be shut of it too!
