Rare coins are like no other collectible. Steeped in history, each possesses a unique background and historical context that captures the imagination. First-time enthusiasts, serious collectors, and professional coin dealers, all involved in numismatics, find great excitement in discovering the qualities that make each coin special.

Over time a coin can change in appearance due to environmental conditions, mishandling and natural forces of decay. You can take an active role in preserving coins for future generations to admire by contacting Numismatic Conservation Services (NCS) so that NCS’ specialists may assist quickly in identifying damaging conditions, and professionally conserve and stabilize your coins.

The expertise of NCS technicians has long been needed in numismatics. Not to be confused with undesirable cleaning, proper numismatic conservation involves examination, scientific analysis and a reliance upon an extensive base of numismatic knowledge to determine the nature of a coin’s state of preservation and the extent of any damage. NCS is uniquely qualified to meet the conservation needs of the hobby.

The Nature of Coins

Eight metals are primarily used in minting coins, tokens and medals: platinum, gold, silver, copper, aluminum, zinc, tin, and nickel. Platinum and gold are considered to be durable and stable but not impervious to damage. Silver, copper, aluminum, zinc, tin, and nickel are more susceptible to environmental damage to their gold counterparts, with tin being the least stable metal. Most coins are made of alloys. Gold and silver, for instance, are usually alloyed with copper. Metals may corrode when in contact with acidic materials and excessive moisture and heat. The effects of corrosion appear differently on each metal or alloy. Tin becomes white and scaly, and may crumble away in your hands.  

Light surface corrosion, or toning as it’s described in the numismatic community, can be very desirable. Collectors often prize it as one indicator of a coin’s originality, or closeness to its original state. Toning causes copper coins to turn brown, and silver and nickel coins to develop hues of blue, red, green, purple, and other colors. Often, these coins need little or no conservation; however, advanced stages of corrosion can damage a coin’s surfaces. If the toning process goes too far, the coins turn black and the actual surface of the coin may be ruined forever.

Traditionally, collectors have been told to never have their coins cleaned; yet this policy stands in stark contrast to many other fields of collectibles. For example, the restoration and conservation of art works is performed routinely. Paintings are not mounted for display with their original beauty hidden beneath layers of dirt and aged varnish. Rather, such debris is painstakingly removed by persons highly skilled in this restoration work. Gems, silver, and other antiques are cleaned and maintained in good order. To do otherwise would be negligent. What should matter is how and why objects are cleaned. Professional coin conservators are no less skilled and responsible than conservators in other fields, so it is time to re-evaluate the cleaning and conservation of coins in this new light. Cleaning removes dirt and agents that hide or might be harmful to an object’s natural and original state. Proper cleaning takes into account original materials and finishes. It studiously avoids damaging original materials and finishes. The overall appearance is enhanced and the coin is more likely to last.

The professionals at NCS are skilled in conservation techniques that can prolong the life of the coins in your collection and, as a side benefit, often enhance their appearance. Combining knowledge of materials science with extensive numismatic experience, they strive to the fullest extent possible to return your coin to its original appearance.

Sometimes confusion arises about the term "conservation." Numismatic conservation involves examination, scientific analysis, and a reliance upon an extensive base of numismatic knowledge to determine the nature of a coin’s state of preservation and the extent of any damage. Conservation also encompasses appropriate procedures to protect the coin’s original appearance and to guard against future deterioration to whatever extent possible.

Professional conservation should not be confused with "Coin Doctoring", in which an attempt is made to improve the appearance and grade of a coin through deceptive means such as artificial toning and where unaccepted or unorthodox methods are employed. Also not qualifying as conservation is restoration where mechanical repairs are made such as filling holes, smoothing out scratches, and re-engraving of detail. It is essential to speak with an NCS professional:

  • when you notice changes in a coin, such as discoloring or spotting
  • before you try to conserve a damaged coin yourself
  • if your coin has been subjected to extreme environmental conditions
  • after you have submitted a coin to a grading service and had it returned with a "no grade" designation for certain reasons such as "PVC," "artificial toning" or "Residue."


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  • Contact Us
  • NCS
    P.O. Box 4750
    Sarasota, FL 34230
  • 1-866-NCS-COIN toll free
    +1 941-360-3996
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    +41 43 816 28 16
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    +49 89 255 47 545

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