Error coins and damage: how to tell them apart

There is one question behind every "is this an error?" post ever written: did it happen inside the Mint, or afterwards? Inside is an error, and errors sell. Afterwards is damage, and damage is worth nothing no matter how strange it looks.

Almost everything people find is the second thing.

Real errors, in rough order of how often they turn up

• Off-centre strike. The blank was not aligned, so part of the design is missing and there is a blank crescent. Value scales with how far off it is and whether the date survives.
• Doubled die. The die itself received a doubled impression when it was made, so every coin from that die shows the same doubling, in the same place, with rounded and separated letters. This is the famous one, and the 1955 Lincoln cent is its poster child.
• Broadstrike. Struck without the collar, so the coin spread wider and has no reeding.
• Clipped planchet. A curved bite out of the edge where blanks overlapped on the strip. Genuine clips show a matching weakness on the opposite rim, which is how fakes are caught.
• Wrong planchet. A dime struck on a cent blank. Rare and immediately obvious on a scale.
• Die crack or cud. A raised line or blob where the die broke. Small money, but real.

The one that fools everybody: machine doubling

Machine doubling looks like a doubled die and is worth nothing. It happens when the die bounces on the way up, shearing the metal it just struck.

The difference is visible with a loupe and is absolute:

• Doubled die: the doubled parts are rounded and full height, like two complete letters overlapping.
• Machine doubling: the doubling is flat and shelf-like, a smeared ledge at the edge of the letter, lower than the letter itself.

If it looks scraped, it is machine doubling. If it looks like two letters, get it checked.

Damage that gets mistaken for value

• Rim dings, gouges, scratches. Post-mint, every time.
• Environmental damage. Green corrosion on copper, black pitting on silver.
• Acid-etched or "spooned" coins. Rolled on a spoon to fatten the rim, sold as broadstrikes.
• PMD lettering. A letter that looks doubled because something hit it.
• Coins found in the ground. Almost always worth less than the same coin from a drawer, however old.
• Cleaned coins. The most expensive kind of damage, because it is usually done on purpose to a coin that was fine.

Why our own catalog hides error records

Error coins share a date and a country with the ordinary strike they came from, so a matcher that goes on the numbers alone will happily bind an ordinary coin to an error record and quote its price. We measured that happening: a common Spanish 5 pesetas showing the price of a mule error, and a Portuguese euro showing $28 to $76 to half a dozen phones.

So a record whose subject names an error is now veiled: it only binds when the scan itself says the error word. A date never opens it, because every error shares its date with the normal coin. It is a small rule that stops a whole class of flattering nonsense.

What to do if you think you have one

Photograph it, both faces, in flat light. Do not clean it, do not rub it, and do not send it anywhere before somebody who does this for a living has seen a picture. Real errors are worth authenticating; damage is worth exactly the postage you did not spend.