Finger Print On Morgan

As already noted if the print has been there for a long period of time it may well have impregnated itself into the metal. Although even that can be removed but will always leave a mark where some of the metal has been also removed. Best leave it sit in Acetone for several days though. An extensive time in Acetone may remove the print either in part of completely. Other solvents would be more succesfull but would leave the coin in a what is known as a cleaned coin. I've had some luck with the jewelery cleaners sold at Walmart in finger print removal but the entire coin came out as really, really cleaned.
The main thing here is the value of the coin prior to cleaning. If it is a common coin, you've got not much to loose. If it's a valuable one, any cleaning may excessively deminish the value.

Yes, acetone is very volitile and will rapidly evaporate....cover it tightly.

Do not seal it tightly. Gasoline is like an inert substance compared to acetone's volatility, and knowing I had a container pressure-sealed against acetone in my house would make me a very nervous boy indeed. Better to just cover an open container with a pane of glass or something, and expect to add acetone over a few days. You'll want to change it after the first 24 hours or so, anyways, to remove whatever has been pulled off the coin into solution.