Yesterday I stopped by my LCS to pick up some silver rounds. He was sold out, so he offered me some ASEs for the same premium as he usually charges for rounds - the catch is, they were covered in some sort of gluey-hardened goop.
I figured silver is silver so bought 'em, thinking that if I cleaned 'em up I'd have gotten an especially good deal.
It appears that at some time in the past somebody used some sort of unknown (to me) substance to attach these to a makeshift display, and whatever it was they used, it doesn't want to budge. It's not hot glue and it's not contact cement. It doesn't respond to acetone, isopropyl alcohol, or goof-off. I've tried a hot-air gun and I've tried freezing them. I even tried old-fashioned soap & water.
I have managed to peel small amounts of this stuff off, but for the most part, they're still covered with areas of thick, hardened material. Where I have peeled some off the coins are nice and shiny & normal looking underneath.
I'm down to either leaving them as-is, or trying to burn the stuff off with a blow torch.
I figure that there is no way I'm going to get the silver hot enough to melt, and I have a hard time thinking this stuff would stand up to a blow torch, but before I take a torch to an ASE, I thought I'd see if anybody else had an opinion about this. The thing I want to avoid is putting a tone on the coins from the heat, which definitely happens when you heat some metals to temper them.
Any input on how to remove unknown hardened stuff from silver coins is appreciated!