Get two short mason jars.
Fold two paper towels a couple of times and line inside of jars.
Fill both jars with about 1/2 inch acetone.
Put on vinyl exam gloves.
Gently put coin in first jar and wait 15 minutes.
Pick up coin by the rim and hold while it air drys.
If finger print is still there take a q-tip, dipped in acetone, than apply gentle pressure on finger print with q-tip.
Put coin gently in second jar for 10 minutes.
Pick up coin by the rim and hold while it air drys.
Done.
If this doesn't work than hammer, chisel and blow torch (in that order). After trying the sandpaper of course.