Hey Gypsyheart, can you post a pic of it, maybe sitting next to a quarter or something to show us the actual size? Your coin may be too dark for us to get a good look at it but the size will surely help us. Just a thought.
You can use a brass brush but, rub very lightly to remove some of the dirt and the put it back in the oil to remove the rest. But be very carefull not to mark the coin with brush