Don't ever clean a coin, unless...

I picked up this 1986 American Silver Eagle at the Local Coin Shop, for $19 (USD). This is one of the few exceptions where one cannot make the coin any worse. The case is not the same as when the wife surprised her husband by polishing his prized rare Silver Dollar collection and reducing the value by 95%. Before: After: An old sock, some red jeweler's rouge, a paper plate and 5 minutes of buffing. But never clean a numismatic or valuable coin or quality coin. Thanks for looking!