Having Residual Concerns About Residue?

Posted on 7/16/2009

A closer look at "residue" on the surface of coins including why this can lead a coin to be rejected for certification and how professional conservation can play a role in bringing these coins back to life.

Having Residual Concerns About Residue? If so, you’re not alone. This subject prompts a great many questions to NGC from its customers. Perhaps the most common is: What does NGC mean by “Residue” when it returns a coin to the customer ungraded? Receiving one’s coin back in the dreaded “body bag,” a flip to which is affixed a sticker revealing the cause for a “No Grade” determination, is mystifying to many customers. More puzzling still is that some coins displaying a naturally occurring film may be deemed gradeable by the experts at NGC. What are the differences between natural, acceptable residue and unnatural or harmful residue which prompts a No Grade judgment from NGC?

The catch-all term “Residue” as used by NGC refers to any one of numerous substances that may build up on a coin. The truth is that even the professional graders at NGC may not know the exact nature of a fine haze that covers a vintage coin, but the important point is that they’re able to distinguish harmless, natural residue from that which is potentially destructive or was applied intentionally to make a coin appear better than it is.

All the many ways that coin “doctors” attempt to conceal problems and the substances they use are subjects for another article. What’s important to know is that, to the trained eye, these problems remain evident underneath the substance covering them. Such coins are among those often sent back to the submitter with a No Grade determination of Residue. In this way, NGC will not reward coin doctors for their efforts, no matter how skillful they may be.

Coin displaying PVC residue
This Peace dollar has a layer of
PVC residue that is easily observed.
Note the “off” color of light green
haze on the coin’s surface. Click
image to enlarge.

Also falling into the No Grade—Residue category are pieces having some film which may have developed naturally but which poses a risk of further deterioration. Most such instances are the result of polyvinyl chloride (PVC) forming over a coin’s surfaces from prolonged storage in soft, vinyl flips. Frequently, in such cases, rather than “Residue,” these coins’ accompanying No Grade tags will read specifically, “PVC.” When the nature of the contaminant is not known, the generic term Residue appears.

Some of the naturally occurring, acceptable residue seen on old coins is simply the result of long-term storage in canvas mint bags, paper bank wrappers, coin albums or other organic media. These materials emit vapors as they react with moisture and the atmosphere. Though the process is very slow, over a period of years some of this vaporized material will settle onto coins or even react with their surfaces. The metals, too, react with moisture and the atmosphere to form toning, which may be either distracting or quite beautiful, depending on its pattern, coloration and depth.

The professional graders at NGC are familiar with all of these circumstances and the resulting appearance of naturally hazed or toned coins. Such considerations are paramount when determining whether or not a coin may be graded. Since each and every NGC-certified coin is backed by NGC’s solid grade guarantee, the company will not grade and encapsulate coins displaying contaminants which may, over time, lessen the coin’s grade. Therefore, any coin which is NGC certified and encapsulated has been determined to be safe from deterioration under normal storage conditions, even if it may exhibit some film on its surfaces.

Many coins which do receive a No Grade determination of Residue are not necessarily hopeless. Residue can often be successfully removed from these coins by professional conservation. Numismatic Conservation Services, LLC (NCS) employs professional conservators specializing in numismatic items. These individuals have both the knowledge and equipment to skillfully conserve coins which are suffering from many harmful residues. Coins which have been body-bagged by NGC for Residue may be submitted to NCS for evaluation; NGC even offers a small rebate if the No Grade tag is included. The NCS submission form includes options for grading following the conservation process, and this has resulted in many a happy ending for previously unattractive or ungradeable coins.

In some instances, a coin graded and encapsulated by NGC will have a different kind of note affixed to the capsule indicating that the experts at NGC have determined it to be a good candidate for conservation. What this means is that, while clearly gradeable as is, the coin’s appearance may be improved through the removal of light residue or unattractive toning. This doesn’t imply that the grade will necessarily be raised after conservation, but the certain result will be a more desirable coin that brings greater pleasure to the owner and will be easier to sell when that time comes.

NCS has an enviable track record in conserving and stabilizing many important coins once considered at risk of further deterioration. A notable recent example is the famous Mickley-Queller specimen of the legendary 1804 silver dollar. For decades this coin was considered to be a lightly circulated piece, due to an unappealing film which impaired its proof surfaces. Submitted to NCS for professional conservation prior to its sale as part of the magnificent Queller Family Collection of silver dollars, NCS intervention revealed this coin to be a delightful, glossy proof which NGC was able to confidently grade PF-62. Furthermore, this coin has been rescued from any further diminishing of its beauty by stabilizing its surfaces through removal of the contaminant film.

So successful has NCS been at restoring and preserving the attractiveness of rare coins that it was selected by the Smithsonian Institution to conserve the premier rarities of the National Numismatic Collection in Washington, DC. These include such magnificent and unique specimens as the 1849 pattern double eagle in gold and the two varieties of the 1877 half union gold fifty-dollar pieces. Formerly at risk of mishandling and atmospheric exposure due to being stored simply in cabinet drawers, these irreplaceable examples of our nation’s numismatic heritage have since been encapsulated by NGC so that they may be safely studied by scholars and admired by coin enthusiasts from around the world. Indeed, all of the Smithsonian’s most important American numismatic rarities are now safely stored within NGC capsules.

Yes, residue can be a problem, or it can be a distinctive badge of antiquity. Knowing the difference sets NGC and NCS apart. Knowing when to ignore residue, when to red flag it and when to remove it skillfully through professional conservation is all part of the NGC and NCS ongoing commitment to numismatics.