What it is
Most "errors" sent to dealers are actually damage that happened after the coin left the Mint. Damage has no collector value and can lower a coin's value.
What causes it
Machines, tools, chemicals, heat, plating, wear and handling.
How to identify it
- Scratches and gouges cut into the coin, leaving displaced metal.
- Discoloration from heat or chemicals, or uneven plating.
- Bent, squeezed or flattened coins with distorted letters.
How to tell it from damage
Genuine errors happen during minting, so the coin's surfaces and the struck design stay crisp and consistent.
Why most error reports turn out to be damage
Coins spend decades in pockets, machines, jars and soil. Every one of those places can change a coin in ways that look unusual. Damage outnumbers genuine errors by a wide margin, because the Mint inspects and screens its output while nothing protects a coin once it is released. The key to sorting them is to ask whether a feature could have formed under the dies at the moment of striking, or only afterward.
The dies strike with great force inside a collar, so anything that happens during minting produces crisp, well-defined metal with consistent texture and luster. Damage happens with far less control. Tools cut and gouge, chemicals eat unevenly and heat discolors the whole coin. Those differences are visible under a simple loupe.
Common kinds of post-mint damage
Mechanical damage includes scratches, gouges, rim dents, bending, squeezing in a vise and flattening on railroad tracks. Coins also pick up marks from counting and wrapping machines, from being used as tools and from being drilled or holed for jewelry.
Chemical damage includes acid dipping, cleaning with harsh polishes, corrosion from moisture or soil and green residue from PVC plastic holders. Heat damage, from fires or deliberate heating with a torch, discolors coins with rainbow or dark tones and can blister copper-plated zinc cents, since zinc melts at about 420 degrees Celsius, roughly 787 degrees Fahrenheit.
Deliberate alterations include plating with gold, silver or chrome, novelty two-headed and two-tailed coins made by machining two coins together, removed or added mint marks and tooled dates.
How damage differs physically from a striking error
Struck metal flows. When the dies close, metal moves outward and upward into the design, leaving smooth surfaces with flow lines and luster. Damage either removes metal or pushes it around without a die to shape it. A scratch removes or displaces metal and leaves raised burrs along its edges. A dent pushes metal down and bulges the surface nearby. A squeeze flattens the high points and stretches lettering.
Raised versus sunken is the simplest rule. Die-related errors such as die cracks, cuds and clash marks are raised on the coin, because they began as recesses in the die. Damage almost always leaves a depression. The only way to add raised metal after minting is to add material, such as solder or glue. That shows up as a seam or a different texture.
A step-by-step routine for a suspected error
Look at the whole coin before focusing on the odd feature. If the coin is worn, scratched or discolored all over, the odd feature is probably part of the same story. Next tilt the coin under one light to see whether the feature is raised or sunken. Then weigh the coin on a scale reading to a hundredth of a gram and measure its diameter. Plating adds weight, acid and grinding remove it and squeezing changes the diameter.
Check the edge and rim. Damage often leaves a flattened rim, tool marks or a seam. Finally compare the coin with photos of the error type you suspect from a reliable reference and list every diagnostic a genuine example should show. If any is missing, treat the coin as damaged until an expert says otherwise.
Damage that most often fools new collectors
Coins with missing reeding have usually been ground or worn rather than struck without a collar. Thin, oversized coins have usually been flattened. Copper-looking clad coins have often been chemically treated rather than missing a layer. Silver-colored cents dated after 1943 are usually plated, which a scale reveals because their weight is normal.
Two-headed and two-tailed coins found in circulation are almost always magician's novelties made by hollowing one coin and fitting another inside. A seam can usually be found just inside the rim. Coins with letters stamped into them, punched initials or embossed shapes were marked after release and have no error status.
How grading services handle damaged coins
Grading services will not certify a damaged coin as a mint error. Most return it ungraded or give it a details grade that names the problem, such as cleaned, environmental damage or altered surface. A genuine error that was later damaged can still be attributed, but the damage is noted and it lowers the coin's appeal to collectors.
Sending a damaged coin for grading in the hope that it is an error rarely pays off. Running through the routine above first, with a scale and a loupe, answers the question for most coins before any fee is spent.
Frequently asked questions
What causes a post-mint damage?
Machines, tools, chemicals, heat, plating, wear and handling.
How can I tell a post-mint damage from damage?
Genuine errors happen during minting, so the coin's surfaces and the struck design stay crisp and consistent.
How can I tell if my coin is an error or damage?
Check whether the odd feature is raised with the same luster as the rest of the coin, which points to the Mint, or sunken with scratches and burrs, which points to damage. Weighing the coin and checking its edge settle most cases.
Is a two-headed coin an error?
No, two-headed coins found in circulation are almost always novelty pieces made by joining two coins. Look for a seam just inside the rim.
Why is my penny silver colored?
Unless it is a 1943 steel cent, a silver-colored penny has almost certainly been plated or coated after it left the Mint. A cent struck on a dime planchet would be smaller and much lighter.