Frank, I'm not an expert so I Googled it and honestly the only thing I did was use ketchup and warm water and gently rolled around a Qtip and it really cleaned it up....obviously It didn't perfectly, but all the little sticky crud came ran right off...
Great find, Just please be careful with Katchup! It will turn a beautiful coin Pink!!!.. A safe alt.. is like mentioned Acetone... followed by Few days sitting in olive oil..
A great product you may want to check out... Specially for the removal of verdigris is called "Verdi Care" its my favorite.. Safe and effective. Came across it on a coin forum i frequent. Coincommunity one of the members invented it.. who's a collector. I love hunting for Wide and Close AM variety's... I still have to check which year is what... lol Thanks for sharing.