So I'm looking to educate myself further on the types of issues we may encounter with coins. The coin below is one I scored from the reject tray of a coinstar machine and it's not worth much at all. This makes it a prime candidate for experimenting with crud removal if possible. What I'm wondering is what am I looking at here? The green stuff is what I'm referencing, is this PVC residue? It currently sits in a mylar 2x2 but who knows where it came from. Or is this some other type of crud? What would be the preferred method or course of action for this coin, and what if it were worth a reasonable amount, would the course of action be the same? I know OF using distilled water, xylene, or acetone but don't really know the instances to use it or not and how long to soak, etc. Mostly just trying to educate myself and perhaps experiment a bit. I've casually collected coins for a long time but never really learned much about stuff like this.