Ok, my brain isn't functioning right this morning. I am thinking about the S/D variety. I don't know about this one.
Yeah, you're gonna have to clean yours up some in order to positively identify it. That crud makes it difficult.
It's about the only acceptable way to clean coins. It doesn't harm the coin in any way like other methods. It only removes certain contaminants. It's not like acid that eats away a small portion of the coin.
I usually start with 10 minutes. I think some people soak for hours or a day. I think it should start to work faster. Just let it soak for the longest you can and then rinse it off. A longer soak won't hurt it any.
I'm by no means an expert but the was a previous thread that said its best to soak copper cents in acetone in a dark area with no light and not to rinse the acetone will evaporate
I think the debate about being on dark was if the acetone would deteriorate in light. In the short amount of time it would be in there soaking, it would be fine. They were talking about leaving the unused portion exposed in light for storage. The rinsing part was debated. One said to use purified water. Another said not to rinse. When its a heavily circulated coin, it wont really matter. Its when you rinse on a high gloss coin that it could leave spots. Also, the coin in this thread is a nickel, not a copper cent.
You need to soak the coin in the acetone for a "period of time". That amount of time just depends on how much gunk is on it. Make sure you cover the container it is in since acetone evaporates very quickly. Then rinse with distilled water and repeat if necessary. Not saying it WILL get the gunk off, but it's worth a try. I had it work on a few coins of mine and not do anything to several others.