Hi Jon, Cleaning coins changes the appearance of the coin, and in most collectors' opinions, it ruins the appearance. The tone changes, and the con becomes unaturally shiny. Therefore, cleaning a coin detracts greatly from its value.  Vinegar is a bad idea, beacause dipping coins in acid makes them really horrible, the tone gets ruined, and yellow stuff forms on the coin, and it can start to smell (thats what happened when i dipped a 1967 penny!).