NGC Conservation: Residue Isn't Just a Problem for Vintage Coins

Posted on 1/14/2025

Modern coins that are suffering from the side-effects of improper storage can benefit from conservation.

Numismatic Guaranty Company® (NGC®) uses a variety of proprietary techniques to remove harmful contaminants, stabilize and protect a coin's surfaces and, in many cases, improve a coin's eye appeal. After coins are conserved, they are then graded and encapsulated. Below are a few highlights of coins that were conserved and graded by NGC recently.

South Korea 1970 Gold 10,000 Won

Long-term storage in soft flips containing PVC will lead to the formation of some unattractive residues. These residues are not only unsightly, but they can lead to the formation of permanent damage to the surface metal. Professional conservation can help to both remove the unattractive residue and prevent any surface damage from occurring. This South Korea 1970 Gold 10,000 Won commemorating President Park Chung Hee was recently submitted for NGC Conservation to remove a residue that had formed in stark geometric patterns on both sides of the coin. Opaque residues such as these can be challenging to remove carefully without creating hairline scratches. The professional conservators at NGC have developed techniques to remove these residues safely. After successful PVC residue removal, this coin was revealed to be bright and lustrous and was subsequently able to grade well with NGC.

South Korea 1970 Gold 10,000 Won
Before conservation
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South Korea 1970 Gold 10,000 Won
After conservation
Click images to enlarge.

South Africa 1991 Silver Rand

While poor long-term storage is often the root cause of residue, for modern issues, the original mint packing can be the primary cause of residue development. This South Africa 1991 Silver Rand commemorating nursing schools was submitted to remove a heavy whitish residue from the surface. Residues such as this on modern issues are often caused by long-term storage in original mint packaging, which often contains questionable materials. Luckily, this coin was able to be conserved, with the heavy residue safely removed without damage to the mirrored surface beneath. This coin was able to grade very well with NGC.

South Africa 1991 Silver Rand
Before conservation
Click images to enlarge.

South Africa 1991 Silver Rand
After conservation
Click images to enlarge.

Modern coins, just like their vintage counterparts, can develop heavy residues that hide the original surface. This Malaysia 1976 Silver 10 Ringgit was recently submitted to address a heavy opaque residue that had developed over the entire surface. The conservators at NGC have developed techniques to address these kinds of residues without damaging the surface of the coin. Following professional conservation, this coin was able to grade well with NGC.

Malaysia 1976 Silver 10 Ringgit

Malaysia 1976 Silver 10 Ringgit
Before conservation
Click images to enlarge.

Malaysia 1976 Silver 10 Ringgit
After conservation
Click images to enlarge.

For more information about NGC, visit NGCcoin.com/ngc-conservation.


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