If your coins are still in circulation, they probably aren’t extremely valuable, but that doesn’t mean you can handle them just any old way. You do, however, have to take special precautions in coin handling.
In general, collectible coins should be handled carefully to avoid the possibility of causing wear or introducing substances that may lead to spots or color changes. Many holders will provide adequate protection for ordinary handling. Before removing a coin from its holder, consider whether it’s really necessary.
Never touch an un-circulated or Proof coin anywhere but the edge. Fingerprints alone may reduce the coin’s grade and consequently its value. Handling on the edge only is mandatory when examining another person’s coins, regardless of grade. Get in the habit of picking up collectible coins by their edges, and it will soon become routine.
When setting a coin down outside of a holder is necessary, place it on a clean, soft surface. A velvet pad is an ideal surface and essential for regular handling of valuable material. A clean soft cloth or clean piece of blank paper may be sufficient for less valuable items. Do not drag coins across any surfaces.
The best piece of advice when it comes to cleaning coins is “don’t do it”. Even when coins look dirty or worn out with age, they are still more valuable than coins which have been newly-cleaned. Over time, coins naturally undergo a process known as toning, when oxygen or sulphur reacts with the metal. While it may not look pretty, the surface under the toning still contains the reflective quality known as mint lustre. Cleaning products will not only remove the lustre, but will add tiny scratches and fibres that will render the coin worthless.
Do Not Clean Your Coins! A coin may look dirty or dark but it’s important to resist the temptation to clean it. Cleaning or rubbing a rare coin can eliminate much of its value. You will not get less for a dirty coin, but you may get much less for a cleaned one.
If you are truly concerned about the condition of a coin, contact a professional coin dealer or conservator for advice on your best options.