This is the best way I have found and it does not touch the patina. Take a coffee cup, pour in half an inch or so of hydrogen peroxide, put it in the microwave for a minute or until boiling, remove from microwave, toss in a few IH's. Let them boil away and soak for a couple hours. Take a soft toothbrush and a tiny bit of dish soap and lightly scrub off remaining dirt. If necessary repeat the process for stubborn dirt. This will remove the hard stuck-on dirt/coating that most IH have, but will leave the patina. Once they are clean and dried out completely they tend to look a bit too dry. Take a q-tip and some olive oil and coat them. This will turn them dark but eventually they will dry and return to the patina color. The q-tip and olive oil can also be a good way to remove remaining stuck on dirt. In my area (SW lower MI) this is the easiest and best way to clean them up. Nothing will take off the thick green corrosion that some get - that stuff becomes part of the coin. Try it, you will like it.
HH - BF
