Post-Mint Damage (PMD)
Post-mint damage is anything that happened to a coin after it was struck: scratches, dents, rim dings, corrosion, heat, chemicals, and the marks left by machines that count, sort, wrap and vend coins. It is not a mint error, and it is a common reason a coin is mistaken for one. Many "is this an error?" questions are answered here.
The name is slightly loose. A little of this damage happens before a coin leaves the Mint — bag marks from coins knocking together in bulk storage, scrapes from conveyors and counters. What makes it post-mint damage is not where it happened but when: after the strike, to a finished coin, by something other than the dies and the press that made it.
Post-mint damage is one of three things that arrive under the same question, and NumisDex keeps them apart because the diagnosis differs. A counterfeit is fabricated. An altered coin is a genuine coin modified on purpose to look rarer. Post-mint damage is incidental: nobody was trying to make the coin look like anything.
How Does It Happen?
Circulation and Handling
Coins knock against each other in bags, rolls, tills and pockets. The result is contact marks (bag marks): small, scattered nicks across the surface. They are normal, they are why so few uncirculated coins grade MS-70, and nobody mistakes them for errors. The damage that does get mistaken comes from harder contact — a coin dropped on concrete, struck against another object, or scraped along a surface — leaving rim dings, flat spots on the edge, scratches and gouges.
Machines
Coin counters, sorters, vending machines and roll wrappers handle coins by the billion, and they leave marks that look too regular to be accidental:
- Roller and sorter marks — parallel, evenly spaced lines, or burnished high points where a coin was squeezed through a tight mechanism.
- Jam damage — gouges and scrapes on the edge, deeper and straighter than ordinary bag marks.
- Crimper damage — known among collectors as the "ring of death". A machine-wrapped roll is closed by crimping its ends, and the crimp can press a ring or a partial arc into the outward face of the end coin, near the rim and on one side only.
Tumbling and Heat
A coin trapped in a dryer, or deliberately put in a rock tumbler, comes out with a peened, battered surface and a rim that can look flattened or spread. Error-Ref describes dryer coins caught between the tubs of industrial dryers and battered cycle after cycle: the designs are pummeled into mush, and metal pushed off the edge and rim lies over the field and the peripheral letters as a thin apron, a loose ring on each face. They are a classic false broadstrike. Fire and heat leave discoloration, a grainy or blistered surface, and on zinc cents a rough, bubbled plating.
Environment and Chemistry
Moisture, acids, skin oils and storage materials attack a coin's surface over time. Verdigris forms green deposits on copper. Corrosion pits and eats away metal. PVC damage — a green, oily film from soft plastic flips — comes from the plasticizer breaking down. On copper-plated zinc cents, zinc exposed through a split in the plating forms a white "zinc bloom" that can push the plating up from beneath, and if the bloom is lost the plating can collapse into the cavity (Error-Ref).
Chemicals also change color. A cent dipped in a reagent can come out silver, gold, black or stripped to its core, and a clad coin soaked in acid can lose its surface. None of this changes what the coin was struck on, which is why weight settles most of these cases.
Deliberate Damage That Is Not Deceptive
Some damage is done on purpose without any intent to fool anyone: coins flattened on railway lines, bent, holed for jewelry, cut, or plated in a chemistry class. When the intent is to fool someone — an added mint mark, a filed-off leg, a whizzed surface passed off as mint luster, a plated 1943 steel cent sold as bronze — the coin belongs under Altered Coin instead.
How to Identify Post-Mint Damage
The governing question: did this happen during the strike, or to the finished coin? Every test below is a way of asking it.
- Does the feature repeat? Anything that happened to a die appears on every coin that die struck, in the same place. Damage happens to one coin and never repeats. If a second example of the feature exists on another coin of the same date, it is a die variety; if it cannot exist, it is not.
- Is the luster continuous? At the strike, metal flows under pressure and the coin's flow lines and luster form around any genuine error. Damage comes afterwards and cuts through them: a scratch breaks the luster, a dent flattens it, corrosion dulls it. Under a 10x loupe, tilt the coin under a single light and watch whether the shine flows across the feature or stops at it.
- Raised or sunken? A die crack, die chip or cud is raised, because it is a void in the die that metal flowed into. A scratch or gouge is sunken. That makes "incuse" a reason for suspicion, but not a verdict: several genuine errors are incuse — a strike through, a brockage, an indent and incuse die deterioration doubling among them.
- Where did the metal go? Damage moves metal; it does not remove it cleanly. A gouge throws up a lip, a ding pushes a bulge into the field beside it, a filed edge leaves burrs. A genuine error leaves no displaced metal, because the dies formed everything at once.
- Both sides, or one? A collar or clip error is visible from both faces at the same clock position, because it involves the whole planchet. A dent or ding shows on one side.
- Weigh it and measure it. Damage cannot add metal, and a coin altered in color has not changed weight. A genuine broadstrike, struck outside the collar, spreads wider than normal with the full design on both faces; a dryer coin's design is battered and its rim metal has been pushed inward, not outward. A genuine wrong planchet or missing cladding error has the weight of the planchet it was struck on; a recolored or acid-stripped coin has the weight of the coin it always was, or less.
Error or Damage?
| What you see | Genuine error | Post-mint damage |
|---|---|---|
| A curved bite out of the edge | Clipped planchet: the rim fades out before the clip, and the rim opposite it is often weak or missing (the Blakesley effect) | Bitten, cut or ground: the rim runs straight into the gap, the opposite rim is normal, and the edge shows tool or tooth marks |
| A flattened, spread rim | Broadstrike: wider than normal, full design on both faces, original surfaces | Dryer or tumbler coin: battered surfaces, rim metal pushed over the field as an apron |
| A step or ring near the rim | Partial collar: a clean step around the edge, seen from both sides | Crimper damage: a pressed ring on one face only |
| A line across the field | Die crack: raised, wandering, touching design elements | Scratch: sunken, straight or gently curved, often with a lip of displaced metal |
| Wrong color | Wrong planchet: wrong weight and often wrong diameter for the coin it should be | Plating, chemical or heat: the weight of the normal coin |
| Bubbles on a cent | Blistered plating at the Mint | Corrosion lifting the plating from beneath, often with pitting nearby |
| Doubled lettering | Doubled die | Not damage at all — usually mechanical doubling, which happens at the strike and is not a die variety |
Notable Examples
Dryer Coins
A common false broadstrike. A coin battered inside a dryer comes out with a peened surface and a rim that looks spread, and it is reasonable to wonder whether it was struck outside its collar. A genuine broadstrike is wider than normal and shows the full design on both faces; on a dryer coin the design is worn to mush and the rim metal has been driven inward over the field.
Bitten and Cut "Clips"
A curved notch in the edge looks like a clipped planchet, and a pair of pliers, a vise or a set of teeth can produce one. The genuine clip is recognized by what happened at the strike: the rim tapers away as it approaches the clip, the rim directly opposite is often weak (Error-Ref notes this can be absent on large clips), design next to the clip may show metal flow, and the clipped edge usually shows a grainy-and-smooth breakaway zone. A damaged coin was struck whole, so its rim and design are complete right up to the break.
The Ring of Death
Crimper damage on the end coin of a machine-wrapped roll: a ring, or part of one, pressed into one face just inside the rim. Its regularity makes it look like a collar error, but it is on one side only and it interrupts the luster rather than forming part of it.
"Silver" and "Gold" Cents
Cents that have been plated or reacted in a chemistry demonstration come out silver or golden and are offered as off-metal errors. A genuine cent struck on another coin's planchet weighs what that planchet weighs; a recolored cent weighs what a cent weighs. The scale answers it.
Collecting Tips
- Assume damage first, and look for the reason it is not. Damage is the explanation to rule out first, and an error has to earn its way past it.
- Damage is not an error. It does not turn a coin into a variety. The grading services return damaged coins in details holders that name the problem.
- Carry a loupe, a scale and a caliper. Ten-power magnification answers the luster and displaced-metal questions; a scale and a caliper answer the off-metal and broadstrike questions in seconds.
- Learn the genuine error, not the damage. There are endless ways to damage a coin and a short list of ways to make an error. Knowing exactly what a real clip, broadstrike or die crack must show is faster than memorizing every form of damage.
- Photograph in raking light. A single light from a low angle shows whether luster flows over a feature or breaks at it — the one photograph that lets someone else help you.