Collecting coins can be a dirty business, and if you want your collection to keep its value, you should keep it that way. No, we’re not talking about counterfeiters and forgers, although they’re out there. And we’re not referring to unscrupulous dealers (but be careful who you buy from). We’re talking about the coins themselves. Because for collectors, dirty can be beautiful. 

Just like most other collectibles, coins retain their value by being kept in their natural state. That includes natural aging such as oxidation and patina. Removing it actually lowers a coin’s value. Even a simple washing can leave scratches and blemishes that degrade the coin’s collectability. So before you even consider cleaning a mud-encrusted coin, be sure you know how to do it without ruining it.

On the other hand, if you’re buying coins, you need to know the telltale signs that it’s been cleaned. Here’s what to look for:

Bright-Looking Older Coins

Circulated coins have a patina that comes from reaction with the elements and contact with skin oils. Cleaning removes most, if not all, of it, giving the coin an unnaturally clean metallic look. Old copper coins should look medium to dark brown with no shine at all. Older silver coins will look greyish and have a patina around the lettering and artwork. They should have little or no luster. 

Dull Uncirculated or About Uncirculated Coins

Uncirculated or AU coins should be bright and lustrous. When held at an angle to strong light, the light should reflect in a radiating cartwheel pattern from the coin’s relief surfaces. Just because an uncirculated coin is bright and shiny doesn’t mean it hasn’t been cleaned, though. The cartwheel pattern comes from residues and artifacts that were on the coin when it was minted. Those will be removed if the coin has been cleaned, resulting in an even, non-radiating luster. 

Some coin cleaning is evident to average collectors with a little close inspection, but sometimes it takes an expert grader to see it. Coins that were cleaned a long time ago may even have regained enough patina to fool them.

Buy from Trustworthy Sellers Only

The safest way to protect yourself from dirty deals on cleaned coins is to buy only from sellers you trust. For particularly valuable coins, it’s a good idea to send them to a professional grading service like PCGS, NGC, or ANACS and get an official stamp of approval. 

For more information about detecting cleaned coins, see this article on the Coin Update website.

For a more general look at the topic, this article on US Coin covers the subject pretty well.

And whether you’re a seasoned collector or just getting started, be sure to browse the selection of U.S. and foreign coins and banknotes available online from The Great American Coin Company. Our inventory is constantly changing, so be sure to check back often.

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Great American Coin Company