The number one mistake new collectors make is confusing post-mint damage with a genuine mint error. This guide breaks down the most common types of damage and explains why they are not errors, with clear comparisons so you can tell the difference.
Post-mint damage (PMD) is anything that happens to a coin after it leaves the mint. This includes being dropped, scratched, cleaned, exposed to chemicals, put through a dryer, or deliberately altered. None of these add value. In fact, they reduce it.
Random lines pressed into the coin surface from contact with hard objects. Scratches are incuse (pressed down into the metal) and vary in depth and direction. A die crack, by contrast, is raised above the surface and follows a consistent path.
Corrosion, verdigris (green deposits on copper), pitting from moisture, and discoloration from chemical exposure. These change the surface chemistry but are not manufacturing defects.
Coins that have been polished, dipped in acid, or scrubbed with abrasives. Cleaning removes the natural luster and leaves telltale hairline scratches in parallel patterns. Professional grading services will mark a coin as "cleaned" and assign a lower value.
Coins tumbled in a clothes dryer develop uniformly rounded rims, random dings across both sides, and a polished or sanded look. They are sometimes mistaken for broadstrikes, but a true broadstrike is wider than normal with no reeding on the edge. Dryer coins are the same diameter as normal.
Coins exposed to fire or extreme heat can discolor, warp, or bubble. The surface takes on an unnatural mottled appearance. This is not a lamination error — lamination involves the metal layers separating during manufacturing.
Coins squeezed in a vice show matching damage on directly opposite spots on both sides. Coins with carved designs, added mint marks, or altered dates are deliberately altered. Neither are errors.
| Feature | Genuine Error | Damage / PMD |
|---|---|---|
| Surface marks | Raised (die cracks, cuds, doubled elements) | Incuse (scratches, gouges, dents) |
| Pattern | Consistent, repeatable across same die | Random, inconsistent |
| Rim | Smooth blank crescent (off-center) or expanded (broadstrike) | Jagged, bent, or locally deformed |
| Color | Wrong metal for denomination (wrong planchet) | Chemical staining, corrosion, toning |
| Weight | Different from normal (wrong planchet, missing clad) | Same as normal coin |
| Both sides affected? | Often yes (strike errors affect both) | Usually random on one side |
If you are not sure whether something is an error or damage, a quick AI scan can help. ErrorHunt is trained to distinguish between common damage patterns and genuine manufacturing defects. For potentially high-value finds, always get a professional opinion from PCGS or NGC before making any decisions.
No. Scratches happen after the coin leaves the mint and are post-mint damage. They do not add value.
Yes. A coin can have a genuine mint error and also have post-mint damage. The error still adds some value, but damage reduces the overall grade and price.
Yes. Cleaning removes the natural surface and luster. Professional grading services note "cleaned" on the holder, which significantly reduces value.
No. Green deposits on copper coins are verdigris, a form of corrosion caused by moisture. It is damage, not a mint error.
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