If it is another metal (due to long contact to another coin) you may have problems getting it of. So best to leave as is. (Or electrolyse it to have fun with alufoil, baking soda and boiling water on top)
If it is another metal (due to long contact to another coin) you may have problems getting it of. So best to leave as is. (Or electrolyse it to have fun with alufoil, baking soda and boiling water on top)