Dear Rainy. That is some good info. I'm totally guilty of the "rubbing the dirt off thing, and now that you mention it, what is dirt anyway, other that a terriffic abrasive. Good stuff, and I agree on the professional being able to tell if you've cleaned it. I used to be in a coin club W A Y, back when you could actually find great coins in your pocket change, and I remember them telling us the same kind of stuff. Be really careful. I've done quit a bit of reading about this on the net, and I'm still pretty leary of trying anything. I used the electo whatever cleaning method and it took a lot of stuff off, but it turned my coins a different color, then some nice person said, "Oh, your'e not supposed to mix copper coins with silver" Gee, what a concept!!! I thought I knew a little more about phisics than that, but I guess not on that day. At any rate, I'm still worried about cleaning with the electrodes, because it might nullify the value of the coin. The Olive Oil sounds like a pretty safe bet, but agin, I bet you wouldn't want to rub too much of the natural look off the coin. Tough stuff to deal with, especiall when a lot of the coins I dig up have a ton of that green, mean patina on them. That stuff is pretty miserable and usually obscures everything, let alone the date of the coin. "What's a mother to do" as the old comercial asks.???? It's good to talk to you about this, because, I think it's a very important subject to anyone wishing to ever sell or trade any of our finds.