Classic copper coins and more recent copper coins are susceptible to dulling residues that obscure their pleasing color.
Numismatic Conservation Services (NCS) 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 by NCS, they are seamlessly transferred to Numismatic Guaranty Company (NGC), an independent affiliate of NCS, for grading and encapsulation.
Below are a few highlights of coins that were recently conserved by NCS and graded by NGC.
Of all the metal types typically used to make coins, coins in copper alloys can be the most sensitive to environmental concerns. Chemicals in the immediate environment can easily turn a red copper coin brown and a residue to corrosion. This Uncirculated 1852 Large cent was recently submitted for NCS conservation to address the development of some clearly noticeable residues. Care must be taken when conserving copper alloy coins as the metal’s sensitivity to the environment also corresponds to sensitivity when conservation techniques are applied. Professional conservation was able to safely remove both the orange residue on the obverse and the green residue on the reverse to reveal a pleasing evenly colored Large cent. This was able to grade well with NGC following conservation.
Long-term storage in inferior coin holders can lead to the development of unattractive and detail obscuring residues. This large bronze 1852 R Italy Papal States five-baiocchi was submitted to remove dulling and detail obscuring residues over much of the surface. Thick residues such as the one on this Italian piece can cause permanent damage. With careful conservation work to remove the dulling residues while retaining the pleasant color of a classic copper coin, this coin was able to grade numerically with NGC following the professional conservation.
More recent copper coins can develop dulling residues just as more classic coins. This copper alloy Proba 1962 one-escudo of the Portuguese colony of St. Thomas and Principe was recently sent to NCS to address a dulling residue that had developed obscuring the lustrous fields. All residues were able to be removed to reveal a lustrous red-brown coin. Following professional conservation, this coin was able to grade well with NGC.
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Press release courtesy of the Numismatic Guaranty Company
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