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Cleaned Copper Coins May Be Challenging to Detect

Posted by David W. Lange, NGC Research Director

This month Dave discusses the difficulty of detecting cleaned copper and bronze coins

My recent column on the mistaken perception held by many that old coin albums will still prompt attractive toning on coins today elicited a great deal of comment from both collectors and dealers. It seems that everyone has an opinion on the matter, and it also suggested another topic of importance with regard to the aesthetic value of coins. This is the subject of cleaned coins, or, more specifically, cleaned copper and bronze coins. These can be extremely difficult to detect, and many a person has been startled to receive a coin back from one of the grading services with the notations “Improperly Cleaned” or “Altered Color”.

The cleaning of copper coins to make them appear mint red seems to have begun as soon as collectors began saving the old large cents and half cents. The cents in particular became quite popular after their discontinuance in 1857, and many a new collector was created at that time. All new hobbyists take some time to develop their taste, and the more perceptive will eventually come to value the appearance of an attractively toned copper or bronze coin. This is especially true when the coins tone to some color other than simply brown. Among my favorites are pieces toned to a vivid steel blue or emerald green. New collectors, however, tend to be disappointed in any unworn coin that does not look just like it did when made, and attempts to restore that appearance have been performed with varying levels of skill for generations.

Many of the large cents and half cents that exist unworn or just lightly worn have been cleaned at some point. The cleaned coins intended for more advanced collectors are usually found with some form of induced toning to mute the bright orange color that typically results. These can be very attractive coins, and in their early years the grading companies may have let a few slip through, though with experience they have since learned to spot such altered color.

More of a problem is the many thousands of small cents and two-cent pieces that have been improperly cleaned.

The wholesale cleaning of such coins began during the 1930s and ‘40s, when the hobby grew in leaps and bounds. The introduction of coin boards and folders created many thousands of new collectors during those years, skewing the hobby population toward inexperienced and unsophisticated buyers. This trend only accelerated in the ’50s and ‘60s. Just as World War II was ending, a series of new chemical coin cleaning products for copper began to appear in hobby publications, and these were widely popular right up through the ’70s and into the early ’80s. It was not until the advent of certified and encapsulated grading in the mid-1980s that the downside of such treatments was revealed. Only then did distinctions begin to be made between original color and restored color, and it became evident just how few pre-1930 copper and bronze coins had survived unmolested.

Since that time many coins have been retoned in an effort to conceal evidence of cleaning, but huge numbers are still offered raw (uncertified) in the marketplace with full, blazing red color. To meet the continuing demand for mint red coins, it appears that new cleaning processes have been developed. These are so deceptive that only an expert can detect original from restored color, and both collectors and dealers may learn the truth only when submitting their coins for certification.

To show how challenging it is to discern modern methods of chemical cleaning I’ll illustrate a coin from my own collection.

About 30 years ago I found this lovely 1916 cent in a dealer’s case and was drawn to it immediately. At that time the coin was blazing mint red, with what seemed to be very convincing color. Of most interest to me, however, was the fact that this cent displayed an amazingly sharp strike from new dies that had no signs of erosion. Indeed, it possessed the detail of a proof. The certification of Lincoln cents was not as common then as it is today, so the fact that this coin was raw did not set off any alarms. A price was agreed upon, and I quickly placed this gem in my type set. A few years later, however, the coin began to tone in a slightly unusual manner that I had not seen in coins known to have original color. I came to suspect that it had been dipped (chemically cleaned), and I would soon have my suspicions confirmed.

I teach a course on collecting USA type coins at the ANA’s Summer Seminar, along with co-instructor Frank Van Valen of Stack’s Bowers. For ease of handling by our students, I try to get all of my type coins encapsulated. Since this Lincoln was still the sharpest one in my collection (being even more detailed than my matte proofs of 1910 and 1913), I had a dealer submit it to NGC with some other coins of his own, knowing full well the outcome. The graders indeed pegged it as having Altered Color. Nevertheless, it remains a great teaching tool, both in developing students’ appreciation for coins of early die state and as an example of very deceptive cleaning.

David W. Lange‘s column, “USA Coin Album,” appears monthly in the Numismatist, the official publication of the American Numismatic Association.

Article re-posted on CoinWeek with permission of NGC

David Lange
David Lange
The author of several books on United States numismatics, David W. Lange received numerous awards and accolades from both the ANA and the NLG. David was the former President of the Pacific Coast Numismatic Society, the California State Numismatic Association, and the New Jersey Numismatic Society. He also had memberships in the ANA, the NLG, the ANS, the LSCC, the EAC, the BCCS, and the Rittenhouse Society. Career highlights included the launching of NGC's Photo Proof and writing historical copy for the United States Mint's website and H.I.P. Pocket Change program for kids. His specialties have included Seated Liberty silver, Philippine coinage under U.S. administration, and British coinage from 1816-1970. In 2007, David published the first comprehensive reference to Coin Collecting Boards of the 1930s and '40s, and for over a decade published Coin Board News four times a year. David Lange died on January 16, 2023. He is missed.

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  1. I have tried a product called Dellers Darkener with some success and alot of work.Have you ever heard of it and do you recommend this type of product? The product restores the aged look to cleaned copper coins. It come in a 1/4 oz.jar.The companies that sells it is “Collecting Supplies from Chester Ct. I cannot locate it on their webpage.What is your expert opinion of this type of product and do you know of any similiar ones.Thank-you

  2. I’ve heard everything from all older copper coins with red or RB have been dipped to the statement that copper/bronze coins can never be dipped correctly. I’m not too sure about this all. I just wouldn’t pay much for old, red copper coin.


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