Mint-made errors

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1999 Lincoln cent depicting wavy steps.

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 should not be confused with coins that have incurred damage after being minted, which is known as post-mint damage (PMD) or post-strike damage (PSD).

Planchet preparation errors[edit]

Blank planchet[edit]

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 or upset rim, which is where the rim becomes slightly raised and rounds off to the center of the planchet. Planchets with upended rims are called type-2 planchets.

A planchet that escapes getting struck (with or without upending) is known as a blank planchet or blank. Depending on the denomination or the issue, type-2 blanks may be worth more than, less than, or the same as, a type-1 blank.

Clipped planchet[edit]

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, which may be straight, curved, ragged, or elliptical.

Lamination flaw[edit]

A lamination flaw is a planchet defect 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[citation needed] become trapped within the planchet.

Hub and die errors[edit]

To produce coins, a mint needs equipment to strike them. They use a steel rod to 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.

Fundamental die-setting error[edit]

A fundamental die-setting error occurs when the die is not set as the producers intended. For example, in April 2013 the Central Bank of Ireland issued a silver €10 commemorative coin in honour of James Joyce that misquoted a famous line from his masterwork Ulysses[3] despite being warned on at least two occasions by the Department of Finance over difficulties with copyright and design.[4]

Missing mintmark[edit]

A missing mintmark error occurs when the mintmark is rendered invisible by 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. This also can occur if the mint simply does not place a mintmark on the coin.[5] A recent example in this category is the 1982 release of about 15,000 Roosevelt dimes without the "P" mintmark.[6] 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.

Doubled die[edit]

Main article: Doubled die
Doubling on LIBERTY from the 1995 doubled die Lincoln cent

A doubled die occurs when a die receives an additional, misaligned impression from the hub. Overdate coins such as the 1942/1 Mercury dime and 1918/7 buffalo nickel are also doubled dies. They are both listed in the CONECA files as class III doubled dies. Class III means the die was hubbed with different "designs" (or hubs that had different dates). They are not repunched dates, since the dates were punched onto the hub.

Die crack[edit]

A coin from a defective die shows a jagged, raised line on its surface, 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[edit]

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[edit]

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

Die clash[edit]

A die clash occurs when the obverse and reverse dies are damaged upon striking 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.[7]

MAD die clash[edit]

1993 MAD clash mark on a U.S. cent

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

Dual mintmark[edit]

A dual mintmark 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.


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 19th-century coins, it is difficult to call an overdate an "error", since it resulted from intentional recycling of the die. Through a similar historical process, mintmarks have been overstamped.

Over mintmark[edit]

An over mintmark occurs when a mintmark is punched into a die and another mintmark punch with a different letter on it is repunched over it. 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". A similar case occurred in 1938, when a reverse die for the buffalo nickel was made for the San Francisco Mint, because that year only, the Denver Mint made these coins with a "D" punched over the "S".

Wrong-sized mintmark[edit]

On rare occasions, the wrong mintmark puncheon has been used on a die, giving a letter 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 Philippines coins.[8] 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.[9] Exactly the same error occurred with the 1905-O Barber dime, although numerous examples are known of this mistake.

Repunched date[edit]

A repunched date 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.

Repunched mintmark[edit]

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.[10] If the image is not strong enough, he will position the punch on the mintmark and punch it a second time. If a misalignment occurs between the first and second images, it will produce doubling of the mintmark, known as a repunched mintmark. A repunched mintmark can result accidentally or intentionally.

Strike errors[edit]

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 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.


Full article: Brockage

A brockage is when a mirror image of a coin is struck on both sides of the planchet. A brockage error typically occurs in the following way: A coin is properly stamped on at least one side, but is not properly ejected. A new planchet is fed, but the former coin overlaps the new blank planchet. When the die strikes the coins, a mirror image of the first coin is sunk into the next coin. The result is an incuse mirror image pressed into the blank planchet. The initial coin may or may not become a capped die. Most brockages are partial and only on one side, but full brockages, where the coins are completely overlapping, are the most desirable.

Multiple strike[edit]

A multiple strike, also referred to as double exposure, 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".

Off center[edit]

An off-center coin is produced when the coin is struck once, albeit off center. Unlike a broadstrike, the punch is not in the center of the coin, but rather the edge. This results in a coin which is not circular. The coin gives a freakish appearance as a result, and various amounts of blank planchet space are visible. The coins can vary in value because of how far off center they are struck, although coins with full dates are more desirable than coins without a date or missing digits.[11]

Struck on wrong planchet[edit]

Sometimes mistakenly classified as a planchet error, a coin struck on an incorrect planchet occurs when mismatched 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. The resulting errors are prized by collectors, though they are usually caught during the manufacturing process and destroyed.

A wrong planchet most often 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 many more different kinds of mules, too many to list, are found.

Wrong-planchet errors may also occur when the composition of the coin changes. Such situations generally arise when the mint has decided to change the alloy or plating of the coin in the new coinage year, but a few planchets from the previous year—and thus of the previous composition—have yet to be struck. Should the dies be changed for the new year while the old planchets are awaiting striking and not removed, coins using the old composition will be struck with the new year's date. Such coins are rare and often highly valued by collectors, as with the 1943 copper cents and 1944 steel cents.

A much rarer error is a denomination struck on a foreign planchet. This did occur occasionally with United States (and before that American colonial) coinage in the 17th, 18th, and 19th centuries, and then very rarely in the 20th century.

Struck through[edit]

A "struck-through" coin is made when an object is set to rest on a planchet before striking. When the dies strike the coin, the object's impression is pressed into the surface of the coin, producing a glaring mark on the surface of the coin. Common examples include staples and cloth. Another good example of a struck-through impression is when die grease fills the crevices of the die, so when the coin is struck, it causes a weak strike, and gives a smudged appearance. A great example of such an error occurred in 1922, when only the Denver mint struck Lincoln cents. The dies were so covered in grease, because the mint had to speed up production, that the mintmark was obscured and therefore either nonexistent or weakened on the 1922 cents. These are very popular with collectors.[12]

Mated pair or set[edit]

A collection of two or more coins struck at the same time or during successive strikes on one or more dies, these coins with the resulting errors are related to one another, fitting together as a set.[13] All brockages, indents, and capped die strikes have a corresponding coin, but are rarely found together. A single coin of the set may be discovered by mint staff during quality control and removed, or the coins may be separated into different lots to be distributed separately into circulation.

Numismatic value of error coins[edit]

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 Australian coin varieties and errors[edit]

  • 1966 "Wavy 2" 20 cents
  • 1979 "Double Bar" 50 cents
  • 1980 "Double Bar" 50 cents
  • 1981 "3-1/2 claw" 20 cents
  • 1994 "Wide Date" 50 cents
  • 2000 "Incused Flag" Millennium 50 cents
  • 2000 $1/10cent Mule
  • 2001 rotated die Centenary of Federation $1
  • 2004 "Pointy A" Large Head 20 cents

Notable U.S. coin varieties and errors[edit]

Notable British Coin errors

1983 "New Pence" two pence 2005 "Pemember" two pound 2008 "Dateless" twenty pence 2011 "Aquatics" fifty pence


  • 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[edit]


  1. ^ Herbert, Alan. Official Price Guide to Mint Errors. New York: House of Collectibles, 2007. 7th ed. p. 2. Print.
  2. ^ "Royal Mint. (2010). "Making the Coins in Your Pocket." Retrieved 5 November 2010 . Para. 2 and 3. Web". Archived from the original on 6 November 2010. Retrieved 2012-04-04. 
  3. ^ "Error in Ulysses line on special €10 coin issued by Central Bank". RTÉ News. 10 April 2013. 
  4. ^ "Bank alerted to Joyce coin risk". Evening Herald. 25 May 2013. 
  5. ^ "Hernandez, Jaime. "1982-The Case of the Missing Mintmark." PCGS, 2009. Retrieved 5 Nov. 2010 . Para. 1. Web". Archived from the original on 6 November 2010. Retrieved 2012-04-04. 
  6. ^ "1982 No P Roosevelt Dimes - Potential Major Rarity!". 2012-03-27. Retrieved 2012-04-04. 
  7. ^ "1955 "Bugs Bunny" Franklin Half Dollar". 2012-03-27. Retrieved 2012-04-04. 
  8. ^ "1945-S Micro S". 2005-01-09. Retrieved 2012-04-04. 
  9. ^ "1892-O BARBER HALF DOLLAR". Retrieved 2012-04-04. 
  10. ^ "Wexler, John. (2010). "Repunched Mint Marks (RPMs) & Over Mint Marks (OMMs)." Retrieved 6 Nov. 2010". Retrieved 2012-04-04. 
  11. ^ "Lincoln Cents with Off-Center strikes". Retrieved 2013-10-25. 
  12. ^ "1922 Weak D and No D Lincoln Cent Varieties". Retrieved 2013-10-25. 
  13. ^ "1979 Canadian 1-Cent Mated Set". CoinTalk. Retrieved 2014-06-15. 

External links[edit]