from coin dealers, that green stuff cannot be removed, no matter what you do. I believe they call it green goo. Really strange, and it is some kind of reaction between the metal and some plastics. Dice do really weird things too in the phoam (board said that if I started that word with a "f", it was a naughty word) that used to be packed between them in the plastic boxes they used to come in.
Jodi CH0009-A
Casino Collectibles