NCS Conservation: A Spanish Colonial Coin Shines after the Removal of Rusty Residue

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 Corporation® (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.

So often treasure coins are cleaned through amateur efforts, resulting in permanent and irreversible damage. It is truly a pleasure when a coin has not been the victim of destructive amateur conservation methods.

This 1751 Santiago Chile struck 8 Escudo arrived at NCS for removal of the heavy red rusty residue that this large gold coin had likely acquired from long-term storage well before it became the prize of a numismatist. Thick residues such as those seen on this important Spanish Colonial piece are frequently found on gold coins around the world. The conservators at NCS have developed specific techniques to address these kinds of red and rusty residues. Following successful residue removal, this Chile 8 Escudo was able to grade well with NGC.

Chile 1751 8 Escudo Before conservation Click images to enlarge.

Chile 1751 8 Escudo After conservation Click images to enlarge.

Residues can form through poor storage as well as from the result of circumstance long before the piece has numismatic value. This 1786 V.O.C. Netherlands East Indies silver 3 Gulden was submitted to NCS for conservation to address the odd brown residues and spots of green that had formed in the recesses of an otherwise evenly toned large silver coin.

The residues seen on this Dutch Colonial coin can frequently be the catalyst for environmental damage. Luckily, this coin was able to have the offending brown residues safely removed without any significant environmental damage remaining. After professional conservation, this coin was able to grade numerically with NGC.

Netherlands East Indies 1786 3 Gulden Before conservation Click images to enlarge.

Netherlands East Indies 1786 3 Gulden After conservation Click images to enlarge.

Of the three most commonly used coinage metals, copper is most susceptible to environmental damage that causes quick toning and corrosion. This bronze 1888/7 A Belgian Congo 5 Centimes was submitted to the conservation professionals at NCS to address the small area of raised green corrosion beginning to notably form on the obverse around 8 o’clock.

Color on coins with a high copper alloy is of utmost importance and taken into consideration when removing dreaded corrosion spots. This Belgian African Colonial coin was able to have the raised green corrosion spot removed, leaving only the slightest evidence behind. NCS also brightened the remainder the of the surface. Following professional conservation this coin was able to grade well with NGC.

Belgian Congo 1888/7 A 5 Centimes Before conservation Click images to enlarge.

Belgian Congo 1888/7 A 5 Centimes After conservation Click images to enlarge.

For more information about NCS, visit NGCcoin.com/NCS.