I really gross crusty dime? Edit - Honestly, it looks as though something was spilled on it and damaged it.
Born and raised in KY. I call it soda, pop, or soda-pop. In that context pop just seemed to have the best ring, lol. I have a lot of different terminology and turns of phrase that I picked up from traveling and watching TV. Its hard to pin down my speach patterns or accent.
Environmental damage. It looks like it was exposed to some sort of liquid that didn't play well with copper/nickel alloys.