I just tumble in soapy water for those coins that I will feed to the credit union coin machine. I don't care what they look like; only that the machine will take them.f they are still crusty, like beach coins, I will give them a quick tumble in silica sand (others use limestone/dolomite sand).
For keepers, I use water and a toothbrush. (I haven't found any keydates or anything that could lose value by microscratching).
For keepers, I use water and a toothbrush. (I haven't found any keydates or anything that could lose value by microscratching).