Hi, I have some gold coins and on two of them, black smudges or spots have appeared after I received them in perfect condition. I've had the coins for years and I'm pretty sure they appeared a few months to a year after receiving them. They haven't gotten any worse since appearing. Anyone know what they are? Is there a way to clean them/remove the spots? The pictures aren't perfect but on the Chinese coin, the black smudge is to the left of the castle. And on the Austrian coin, the spot is right in the middle of the organ.
I'm 99% sure they're not. The one on the Chinese coin is a smudge of something and one on the Austrian coin looks like a stain or something.
Gold is almost inert, so I'm pretty sure it's not any kind of oxidation. I'd pop 'em out of the capsules and give 'em an acetone bath. Worst case scenario, it won't hurt the coins.
