Generally it's not a good idea to clean coins.
<<long-time coin collector here.
Water to remove ordinary dirt doesn't hurt, but anything stronger than water, no.
If a coin's excessively worn or damaged in some way, it's "okay" to mess with it, using stuff stronger than water, because an excessively worn or damaged coin isn't worth much anyway.
A hint for those with Indian Head (or Buffalo) five-cent pieces made 1913-1937, where the date's worn off.
The dates on Indian Head nickels were struck in high relief, and thus wore away quickly; I'm sure just about everybody's seen one of those dateless five-cent pieces.
Put a little less than a drop of nitric acid where the date used to be, and the coin corrodes in such a manner that the date reappears. And then of course use water to wash away the acid, once the date's clear.
This will not work on silver coins; don't even try it. It will however work on nickel coins (actually, mostly copper with some nickel in it).
Yikes, I have been using borax and dish soap to soak the Penny's, so far 5 wheat Penny's all dated 1941, should be pure copper as it was a year or so before the War caused a change in the copper content. I tried a magnent and the coin didn't respond
Mom is bringing over a box of change that her father collected as a teenager, 1915 or so.
I think I need a kids microscope as none of our hand held magnifiers are strong enough for my eyesight or hubby's,
.I wonder what the jail time would be for me to beat up the designer of the $1.00 coins that are the size of quarters, how much money we all have lost due to using them as quarters in vending machines and as change buying for a small item, or throwing into the bell ringers kettles at Xmas.
Surprising the amount of foreign coins the size of quarters get into the market place, so far Indonesia, Canada, and one coin so black I have it soaking in olive oil.
Thanks for your information Frank, have you got any good finds?????