Mint-made errors

Mint-made errors

Mint-made errors are errors in a coin made by the mint during the minting process. Mint error coins can be the result of deterioration of the minting equipment, accidents or malfunctions during the minting process, or intentional interventions by mint personnel.[1] Accidental error coins are perhaps the most numerous and in modern minting are usually very rare, making them valuable to numismatists. Intentional intervention by mint personnel does not necessarily include a deliberate attempt to create an error, but usually involves an action intended to improve quality that miscarries and creates error coins instead. Errors can occur during three different stages of the coining process: the preparing of the planchets, the preparing of the dies, and the striking of the coin. Authentic error coins must not be confused with coins that have incurred damage after being minted, known as post mint damage (PMD) or post strike damage (PSD).


Planchet preparation errors

To prepare planchets on which to strike coins, a mint first purchases strips of metal of the correct composition of the coin to be produced. These strips are fed through a blanking machine that cuts them into the metal disks on which the coins are struck, which are known as blanks or planchets.[2] The shape of the coin, whether it be circular, rectangular, or any other shape, is determined by the manner in which the blanking machine shapes the planchets. At this stage, the blanks are type 1 blanks. Next, these type 1 blanks go into an upending mill, which gives the blanks an upended rim, which is where the rim becomes slightly raised and rounds off to the center of the planchet. Plancehts with upended rims are called type 2 planchets.

Clipped planchet

Occasionally a misfeed can occur where the strip of metal is not fed through the blanking machine far enough. When this happens, the punches strike an area of the strip which overlaps the hole left by the previous strike. The result is a blank with a piece missing, which is called a clipped planchet. A clipped planchet may be straight, curved, ragged, or elliptical.


A lamination is a planchet defect (see definition of "Planchet" under "Terms") originating when a portion of the coin metal separates from itself due to impurities or internal stresses. Lamination flaws occur primarily when foreign materials or gas oxide become trapped within the planchet.

Hub and die errors

In order to produce coins, a mint needs something to strike it with. They take a steel rod and imprint the coin's design in it with a hub bearing a relief image of the design.

Hub and die errors are collectively known as varieties. If damage or some form of alteration is made to a hub or die, it is classified a variety. Modern coins are still released with hub and die errors, mainly because the defects are usually too small to be seen with the naked eye. A few exceptions exist, where the dies are used despite producing easily visible flaws. The 1955 Lincoln cent is an example.

Missing mintmark

A missing mintmark error occurs when the mintmark is rendered invisible via one of three identified ways. If the mintmark on the die is filled, plugging up the cavity into which the planchet's metal flows under the pressure of the strike, the mintmark will be weak or invisible. The 1922 no D mintmark Lincoln cents are results of this phenomenon. The other way this can occur is if the mint simply does not place a mintmark on the coin.[3] A recent example that fits in this category is the 1982 release of about 15,000 Roosevelt dimes without the "P" mintmark.[4] Additionally, if the mintmark on the die is filled, the mintmark will be missing. Missing mintmarks can be caused by equipment deterioration, accidents or malfunctions, or intentional intervention.

Die crack

A coin from a defective die shows a jagged, raised line on its surface. This is caused by a crack in the die used to strike the planchet. In U.S. coinage, many coins from the Morgan Dollar series show slight die cracks.

Die break

Coins sometimes show a raised, unstruck area resulting from a break in the die, which is known as a cud mark if it touches the rim.

Die chip

If part of the die chips out, showing as a raised, unstruck area on the coin, it is called a chip.

Die clash

A die clash occurs when the obverse and reverse dies strike each other because a planchet is not between them. Due to the tremendous pressure used, the parts of the image of one die may be impressed on the other. When planchets are then fed between them the resulting coins receive the distorted image. A well- known example is the "Bugs Bunny" Franklin Half Dollar of 1955, where part of the eagle's wing from the reverse gives Franklin the image of protruding teeth.[5]

1993 MAD clash mark on a U.S. cent

MAD die clash

A MAD die clash occurs when an obverse and reverse die strike each other while misaligned in relation to each other.

Doubling on LIBERTY from the 1995 doubled die Lincoln cent.

Doubled die

A doubled die occurs when a die receives an additional, misaligned impression from the hub.

Dual mintmark (DMM)

A dual mintmark (DMM) occurs when a mintmark is punched into a die and another mintmark punch with a different letter on it is repunched anywhere else on the coin except on top of it. See Over Mintmark.

Overdate (OVD)

In the past, it was a common practice for a mint to use a certain die until it broke. As some dies would last for multiple years, a figure would be punched over the old date. For example, some 1942 Mercury dimes show a 1 beneath the 2. For 19th century coins it is difficult to call an overdate an "error", since it resulted from intentional recycling of the die. In more modern times the examples were due to mistakes by the mint. Through a similar historical process mintmarks have been overstamped (see Over Mintmarks). A well known example is the 1900 Morgan silver dollar, when reverse dies with "CC" below the eagle were sent from the Carson City mint to the New Orleans Mint where they were given an "O". (See Repunched Date).

Over mintmark (OMM)

An over mintmark (OMM) occurs when a mintmark is punched into a die and another mintmark punch with a different letter on it is repunched over it. See Dual Mintmark.

Wrong sized mintmark

On rare occasions the wrong mintmark puncheon has been used on a die, giving a letter that's obviously too small. (This is different from planned changes in letter shapes or sizes, which has occurred several times in recent coinage history.) The best known example may be the 1945-S "Micro S" Mercury dime, when the mint used an old puncheon intended for Philippine coins.[6] A much rarer example is the 1892-O "Micro O" Barber half dollar, which may have come about from the brief use of a mintmark puncheon intended for the quarter.[7]

Repunched date (RPD)

A repunched date (RPD) occurs when a date or date digit is punched twice into the die with a misalignment between punchings. This can be either accidental or intentional. See Overdate.

Repunched mintmark (RPM)

A die technician takes a punch, a small steel rod with the mintmark letter on it, positions the punch where the mintmark is supposed to go on the die, and punches it into the die with a hammer.[8] If the image is not strong enough, he will position the punch on the mintmark and punch it a second time. If there was a misalignment between the first image and the second image, it will produce doubling of the mintmark, known as a repunched mintmark (RPM). A repunched mintmark can result accidentally or intentionally. See Over Mintmark.

Strike errors

Strike errors occur when the planchet is struck. It is a fault in the manufacturing process rather than in either the die or the planchet. Numismatists often prize strike error coins over perfectly struck examples, which tend to be more common, but less highly than die error coins, which are usually rarer, making them valuable.


A standard type of strike error is a broadstrike, where the rim image is not struck into the coin's edge because the collar die was missing. Broadstrike errors are produced when the collar die (The circular die surrounding the lower die) malfunctions. The collar die normally applies the edge device (reeded edge, plain edge) and prevents the metal of the coin from flowing outside of the confines of the die. When the collar is prevented from working properly during striking, it may rest below the surface of the anvil die. All denominations of U.S. coins with a broadstrike will have a plain edge.


A brockage is when a mirror image of a coin is struck on both sides of the planchet. This error typically occurs when a coin remains on either die after striking. The second coin receives the image from the die, though its blank other side also receives the image of the struck coin, and the result is an incuse mirror image.

Multiple strike

This occurs when the coin has an additional image on one side from being struck again, off center. The result is sometimes mistaken as being a "doubled die". Note: Also referred to as 'double exposure'

Struck on wrong planchet

Sometimes mistakenly classified a planchet error, a coin that is struck on an incorrect planchet occurs when the wrong planchets are fed into a coin-stamping press. This results in a coin that has been stamped with a design intended for a differently sized coin. In addition, unminted or blank planchets are occasionally produced. The results are usually obvious errors that are also prized by collectors, though the errors are usually caught in manufacturing and destroyed.

A wrong planchet occurs when a denomination is struck on a planchet of a different denomination.Some examples include cents struck on dime planchets, nickels on cent planchets, or quarters on dime planchets. Sacagawea dollars have been reported with statehood quarter designs on the reverse. This type of error is called a mule and there are many more different kinds of mules, too many to list, however.

A much rarer error is a U.S denomination struck on a foreign planchet (17th, 18th, and 19th centuries, and very rarely 20th century).

Numismatic value of error coins

Most error coins demand a premium when sold, if they are modern coins, dependent upon the rarity of the type of error as well as the rarity of that type of error on a particular denomination. Overdates, particularly of 20th century coins, are in demand but other errors may be very minor or of interest only to specialists. The value of error coins has been subject to much debate and the value is usually determined between the dealer and the collector. Conversely, errors on ancient, medieval and higher value coins are usually detrimental to the coin's numismatic value.

Notable U.S. coin varieties and errors


  • Blank. A round piece of metal on which a coin can be struck. Type 1 blanks have a smooth edge, but type 2 blanks have an upended edge. See Planchet.
  • Die. A steel rod used to strike coins. It bears a negative image of the coin design to be struck.
  • Planchet. A round piece of metal on which a coin can be struck. Type 1 planchets have a smooth edge, but type 2 planchets have an upended edge. See Blank.
  • PUP. Pick Up Point. The area on the coin that shows the most prominent effects of the error. Normally used to describe hub and die errors.

See also

  • Coin die
  • Doubled die
  • Die deterioration doubling
  • Wavy steps and Trails


External links

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