The higher the coin grade, then the higher its value should be. Proper coin handling helps to reduce the risk of putting any harmful substances that may lead to spots or changes in the coin’s color, to help retain its value and grade. The coins you cherish and collect should always be carefully handled, in order to reduce the possibility of causing unnecessary wear and tear on these. Highly-valued coins (see how to value your coins here) should as well, be properly cared for, because they will be given a 'coin grade' (see this guide to grading coins) depending on its actual condition and state, and its price as well would be determined by the grade.
Uncirculated or 'Proof' coins should never be touched or clumsily handled. These should also not be held on the edges, since mere fingerprints may do a lot of damage, and reduce not only the coin grade but the coin value as well. Whenever you need to place down a coin outside of its holder, ensure that it’s laid down on a clean and soft surface. You may also lay down a coin on a soft velvet pad, or on a clean, soft cloth or sheet of paper. In addition, avoid holding coins in front of your mouth, because small amounts of moisture could lead to the formation of spots on the coin’s surface. More importantly, you should never drag coins across any surfaces, so that you would avoid scratching or tearing its edges.
Some collectors even wear clean white cloth or surgical gloves when handling valuable or rare coins, to make sure that their coin collections remain neat, shiny and in tiptop shape. A number of specialized coin holders are available today, and these help to provide adequate protection to the coin, and ensure it stays prized and valuable.
While you may think that clean and shiny coins offer better value, the most seasoned of collectors would rather opt to have coins that retain their original appearance, since unsafely cleaning a coin may lead to a reduction of its value by half or more. Wiping a coin is also seen as a no-no, because even using a soft cloth would be enough to cause tiny, minute scratches on its surface. Properly cleaning coins should be done in a manner that is comparable to the way an art collector tries to restore a classic masterpiece. If unsure, coin cleaning should then be best left to the professional cleaners, who have the skill and experience in different coin cleaning techniques. Some expert cleaners for example, soak a coin in olive oil or soapy water for days, to safely remove dirt and other foreign substances, and then rinse these with tap water and then dry it with compressed air.
Expert coin collectors stress that coins normally go through a natural process called 'toning' which refers to a chemical reaction wherein the atoms on the coin’s surface react with sulfur compounds, often leading to the tarnishing of the coin’s surface. This is a non-reversible process however, although some professional collectors indicate that the coin may be repaired through a dipping process, which should strip the unwanted particles or substances from the coin’s surface. Natural toning, on the other hand, may also help towards increasing a coin’s value.