Collectible coins are comprised of three metals and gold, silver, and copper alloys. It is important to protect valuable coins from damage by storing them in cool, dry, and pollution free places. Dampness and pollution may damage valuable, ancient coins. For example, archaeological coins made of copper and its alloys may accumulate chloride ions, resulting in “bronze disease.” Other pollutants that may tarnish copper and silver coins include pollutants containing hydrogen sulphide and the emission of some sulphur-containing organic compounds found in some paints, textiles, and other household materials.
Choosing the proper storage container is very important to retaining the value of collectible coins. Storage containers are available for individual coins, groups of coins, or an entire collection. Place packets of silica gel in the chosen storage container to absorb moisture. Chose a storage place that maintains moderate to low temperature and low humidity to preserve and store coins for a long time.
Store coins in original mint holders, or use archival quality storage containers that may include 2”x2” cardboard/mylar holders, non-PVC clear holders, tubes, or archival storage books. Use plastic coin boxes for groups of coins or collections and store individual coins in holders or sleeves. Folders and albums are available for series and type sets. Use coin tubes and hard plastic holders for long-term storage. Collectors also have the option to invest in a reliable grading service that will “slab” or encapsulate the coins in hard plastic.
The best approach to holding a coin without damaging it is to hold it by the edges while refraining from touching the coin’s face. It is important to handle a coin with care to avoid scratching, polishing, or rubbing the surface of a coin. Use cotton gloves to avoid degrading the value of a coin from fingerprints and human hand oils. Establish a safe working surface and use clean hands to handle the coins by the edges to examine a coin more closely after removing it from its container.
To avoid devaluation of a coin, minimize cleaning the coin. Cleaned coins will lose value when compared with mint state, uncleaned coins. An experienced numismatist should clean the coins if it is necessary for conservation purposes or if the cleaning will increase the coin’s value and appeal.