How to Recognize Cleaned Coins

Cleaning is the most common form of coin alteration that collectors encounter. Its prevalence is widespread and can decrease a coin’s value by 50 percent or more, with extreme cases going down to 90 percent, depending on the coin and the severity of the cleaning. With that, a collector’s ability to understand how coins are cleaned and how it can be identified becomes essential. Three of the most common types of cleaning are abrasive cleaning, polishing, and dipping. While these methods differ, they all permanently alter a coin’s surface and originality.

Abrasive Cleaning

Abrasive cleaning is a process that physically scrapes metal off a coin’s surface, leaving behind hairline scratches. This is the most common form of cleaning and is often done unintentionally. Many coins are rubbed with cloths, tissues, paper towels, etc., with the beholder having the mistaken belief that these “soft” materials are harmless and can remove some unwanted substance from a coin’s surface. In reality, this wiping or rubbing risks damaging the coin and leaving behind fine hairline scratches. These hairlines can reach across the field into device areas, instead of conforming to natural wear patterns. Hairlines can be present on isolated patches of a coin rather than the entire surface when a spot or stained area is targeted. Uncirculated coins are especially harmed by this process, as the flow lines that make up a coin’s natural mint luster are delicate and easily disrupted. Hairlines also show up more prominently on uncirculated examples when tilted in the light. It is important to note that abrasive hairlines should not be confused with die-polish lines. The most notable differentiator is that die-polish lines are raised, while abraded hairlines are recessed. It’s also rare for die polish to occur on device areas of coins.

Dipping

Dipping involves applying a chemical solution to a coin’s surface and removing a thin layer of metal. This method is most commonly used on older silver coins to remove toning, oxidation, or tarnish. This attempt to erase the passage of time gives the coin an unnatural brightness unbefitting of its age. A dipped uncirculated Morgan dollar can appear as if it were minted yesterday, ignoring over a century of environmental exposure. Dipped circulated examples display oddly bright surfaces; where there should be dirt and grime, there’s bare metal instead. Many times, coins are dipped more than once or for extended periods. Overdipping coins creates flat, lifeless luster and a washed-out or chalky appearance, as the more a coin is exposed to the chemical mixture, the more surface metal is removed and the more damage occurs. Although dipped coins, done gently, can still be accepted and straight graded by grading companies, it more often than not decreases a coin’s numerical grade as it sacrifices originality, and the dipping can reveal scratches and abrasions hidden by natural processes like toning.

Polishing

Polishing is a deliberate form of cleaning that’s intended to create a shine on a coin rather than preserve it. Polishing involves repeated abrasion that removes metal to smooth the surface and increase reflectivity. Original flow lines are largely removed by this process to produce a glassy, uniform reflectivity. The abrasions also round out devices, lettering, and numbers, often missing the field area directly below. Polished coins mimic and can be mistaken for proof or prooflike examples, but lack the depth of reflectiveness and surface structure of true proof and prooflike strikes. As with abrasive cleaning, the entire coin is usually affected, so the bust of the coin also becomes abnormally shiny and reflective, even when compared to proof coins. While polishing is an acceptable practice in the jeweler’s toolkit, this does not carry over to coins, where greater emphasis is placed on originality.

Look Everywhere

Two general tips that can be helpful in evaluating potential cleaning are to examine the rim of the coin in question and areas of complex relief. These places are more difficult to reach during cleaning, and the rim is often ignored completely. A coin that displays bright fields but has a toned rim or debris trapped near lettering should raise suspicion as being a potentially cleaned coin. These alone are not conclusive, but they serve as important red flags.

Cleaning is, unfortunately, a common practice in numismatics, often performed without truly understanding its consequences. Because cleaning alters a coin’s surface and originality permanently, understanding how to recognize it is essential to building your collection.