This seller just started piecing out what looks like a fairly extensive dime collection: coins us Mercury Dimes. KEY 1921 and 1921-D He's listed a full set of Roosies, most of the Mercs, a number of Barbers, and even a couple of Seated Liberty. All of them are pictured in Harco Coinmaster plastic strips. Those strips were made with very bad PVC, and most of the coins are showing blue-green "Coinmaster algae" deposits. That's copper and silver that's been dissolved out of the coins by acid from the plastic, never to return. I don't especially collect old albums, and I'm perfectly willing to sell them off to people who do -- but I don't think I could bring myself to sell any of the old Coinmaster albums I've received, just because I'm afraid someone might put coins in them again.
I think I'd go with "delicate sea-green patina", as in "don't touch it because it'll stick to your finger".
To their side, they did offer non-PVC replacement strips once they became cognizant of the problem to people who purchased them directly from company in the 80s. They were the only company I know that owned up to the problem of PVC.
I rescued a BU Roosevelt collection (46-78 incl. S proofs) from a Harco album and put it in a blank Dansco dime album. The inner sleeves didn't seem to have PVC, but there were a couple coins that needed to be soaked in acetone. Rather than continue the set going forward, I decided to go backward and add Mercury dimes to the album. Only 30 years of those rather than 40 years of Roosevelt dimes I'm missing from the album.
After all, they certainly didn't get to their present state of preservation by having people paw over them...
