marcomo said:
To clean or not to clean, it's a matter of personal preference. It's not like it makes any difference in value with common date coins.
Now if you ever find a Barber dime dated 1894-S, trust me on this, don't clean it!
Its really according to the coin, I mean coins (US coins) are graded by condition and detail, that means that dark gray silver with good to strong detail can be clean back to a soft silver
once without degrading it!
Now copper or bronze coins that is corroded is already in POOR condition, and its the metal that is corroded, so often times (most times) you can't do much cleaning without
a HIGH lost of metal, many times in this condition a coin may have a tad of a readable date and after cleaning it won't.
There is NO increase in value to a coin for "patina" like a vintage brass clock.
Now, there are coin shops that will try and rob you if they no you found the coin metal detecting and you've cleaned it, but a lot of them are like a lot of car salesman, what you have has no value,
and their stuff is the greatest, your coin don't have much value, until it becomes theirs for resale!
Silver or gold coins can be cleaned IF the process don't remove enough detail to take the coin to the next lower grade for the coin.
Very POOR, very little detail, exceptionally RARE coins should be handled WITH UP MOST CARE!! cleaning or otherwise! A mistake and it could become worthless!!!!!!
Mark