Here’s my coin-washing story:
I’ve always made a point of stopping to pick up any coins I see on the street—even pennies, because it all adds up, right? I like to set them all aside, separate from my regular pocket change, and watch them add up. Some of the coins are pretty dirty, especially the ones that have been kicking around in the road.
At some point I had about $90 worth of found coins and decided to wash them all. But soaking them in a pan of dish soap and water didn’t get the oily street-gunk off them. For some reason I thought that using vinegar might help—I mean, I use it to clean things around the house all the time, right? So I put vinegar in the pan with all the coins and let it sit for a while…
You guessed it: I wound up with a whole bunch of very-blotchily copper-plated non-penny coins 
