Cleaning a penny with rough grime on it
 

Hey,
I recently dug up a penny with some rough grime on it. It looked almost impossible to get off, but I didn't do anything to it because I did not want to ruin the coin too much. The coin is unreadable. Nothing on it is visible. How do I go forth cleaning this safely?

Thanks!

Start with warm water, dish soap and a toothbrush

I like to let them soak in water for a few days. Sometimes it softens the grime enough to clean off using a water spray or a light rub from a splintered toothpick. If it doesn't work then no harm done and you can still try other things if you want.

Ditto +2 Warm water and dish soap. Don't be in a hurry. Some of that crud will soften up over a few days.
Use the wooden toothpick as described after that to see if it is releasable.

Note: If it's a zinc cent, it most likely will be internal corrosion and that is a dead end for the zincoln.

Leave it as is and tell everyone its an 1859 Indian head. When they ask how you know it is, ask them how they know it isn't.