If they're old circulated coins with organic gunk trapped in the devices, then an acetone soak might be in order. Other than that, do nothing.
Yes, and there are many, many threads discussing the methods. This one for example - https://www.cointalk.com/threads/proper-acetone-procedure.193708/ But there are many others as well. To find them, simply do a search using "proper cleaning" as your key words. That will likely bring up far more than you even want to read. If you wish to narrow that down a bit, put my user name in the Posted By Member box.
A few months ago, I decided to google how to clean pennies and I kept reading about apple cider vinegar and salt. I was Leary about it so I tried it on just a few and at first looked like it worked until they dried and had no luster at all then within weeks they turned green! I didn't want to repeat another mistake with Google, so I figured I would ask you fine gentleman!
If they are just plain old silver coins (dimes, quarters, halves from the 40s to early 60s), there is no point in cleaning them. They are worth their silver value whether cleaned or not. If they are older than that, it depends on the date and mint mark, but in most cases, the same rule applies.
