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. Coins with similar characteristics are known as varieties. The term variety is sometimes used to refer to coins with both intended and unintended differences. The term error refers only to coins with unintended differences. Not all errors are varieties as there may be many examples of a specific error, or the error may be unique. For example, there may be many indistinguishable examples of a specific die crack, while an off-center strike may be unique. Being unique does not mean that an error is valuable. Although no other coin may be identical to a specific example of an off-center strike, off-center strikes happen often enough that buyers can choose from many examples each of which varies from the other.

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 be the result of defective planchets, improperly prepared, installed or deteriorated dies or the result of mistakes made during striking.

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

Planchet preparation errors[edit]

Dime type-one blank and one cent type-two blank

Blank planchet[edit]

Mints purchase long strips of metal which are fed through blanking machines that punch out disks known as blank planchets (or simply as planchets or blanks)[2]on which coins are struck. This determines the size and shape of eventual coins. These disks are known as "type-1 blanks (or planchets)". The disks are called "type-2 blanks (or planchets)" after an upending mill adds uniform, rounded rims. Type-2 blanks may also be considered striking errors as they are prepared correctly, but are released without having been struck.

Clipped planchet

Clipped planchet[edit]

A misfeed can occur when the metal strip is fed through the blanking machine. The punches sometimes overlap the leading edge of the metal producing a straight clip. Sometimes, the punches strike an area of the strip which overlaps the hole left by the previous strike producing a curved clip. Sometimes multiple overlaps produce elliptical clips, and other times the punches strike the irregular trailing edge of the metal strip producing irregular clips.

Improper planchet thickness[edit]

Coins are sometimes struck on planchets that are either too thin or too thick producing underweight or overweight coins. This can be because the equipment is set improperly or because the metal strip was intended for another coin denomination such as a quarter planchet cut from metal intended for dimes.

Pealed lamination

Lamination flaws[edit]

A lamination flaw is a planchet defect that results from metal impurities or internal stresses. Lamination flaws can cause discoloration, uneven surfaces, pealing, or splitting.

Hub and die errors[edit]

Mints use hubs bearing raised images similar to the images that appear on a coin to imprint indented images onto steel rods. Those rods becomes the dies which strike planchets making them into coins.

Hub and die errors can occur at the time dies are made, when the dies are installed into presses, and from die deterioration during use. 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 obvious 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 design elements[edit]

Missing mintmarks, dates, and other design elements occur when the mint simply does not incorporate the element on the die and when foreign matter, such as grease, plugs the cavity into which the planchet's metal flows under the striking pressure. Tilted dies also can cause missing design elements. See misaligned dies below.

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.

A die crack is seen to the left of Lincoln's head

Die crack[edit]

Dies can crack during use. The crack appears as a jagged, raised line on the surface of subsequently struck coins. In U.S. coinage, many coins from the Morgan dollar series show slight die cracks.

Broken die resulting in a "cud" atop Jefferson's head

Die break[edit]

Sometimes a portion of a die breaks away resulting in a raised, unstruck area along the edge of subsequently struck coins. This area is known as a cud.

Die chip[edit]

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

The marks seen above the word LIBERTY were caused by the observe die clashing with elements on the reverse die intended to impress the space between the memorial columns

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.[5]

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. Additional misalignment errors are discussed below.

Punching errors[edit]

Some dies are made without mintmarks or dates to permit their use at different mints and in later years. A die technician later adds dates and mintmarks by positioning a punch, a small steel rod with a letter or number on it, and striking the punch with a hammer pressing the image into the die. If the image is not strong enough, the technician will punch it a second time. Punches placed in a different position between strikes will produce a doubled image which is called a repunched date or mintmark.[6] Dual punches occur when punching is repeated in a second location. Sometimes technicians use a punch with the wrong or incorrectly sized letter or number. A well known example of a small mint mark is 1945-S "Micro S" Mercury dime, when the mint used an old puncheon intended for Philippines coins.[7] 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.[8] Exactly the same error occurred with the 1905-O Barber dime, although numerous examples are known of this mistake.

Overdates and over mintmarks[edit]

In the past, mints used dies until they broke. At the beginning of the year, the new date was punched over the old date. For 19th-century coins, it is difficult to call an overdate an "error", as it resulted from intentional recycling of the die. An over mintmarkoccurs when a second mintmark is punched over an earlier mintmark with a different letter. 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".


Lines, called trails, transfer to coins from dies made using the modern high pressure “single pressing” process. When images are impressed into dies using the process, the displaced metal moves out into fields leaving visible lines on the dies. The dies themselves are called trail dies. Coins on which the lines appear are simply called trails.

Wavy steps[edit]

Trails (defined above) were first noted on Lincoln Memorial steps found on the reverse of one cent coins. The trails gave the steps the appearance of being wavy. The term wavy steps is still used to refer to trails found on the Lincoln Memorial steps, but the term trails is more commonly used to refer to lines found elsewhere. See image at the beginning of this article.


Main article: Mule (coin)

A coin struck using dies never intended for use together is called a "mule." An example is a coin struck with dies designed for different coin denominations.

Because of misalignment, the observe of this coin is off-center but the reverse is centered
Uncentered strike reverse.jpg

Misaligned dies[edit]

Dies must be properly aligned in presses for coins to be struck correctly. Errors occur when dies are offset, tilted, or rotated. Offset errors occur when dies are not centered one over the other resulting in one side of a coin, but not both sides, being struck off-center. Tilting errors occur when die surfaces are not parallel producing coins that are thinner along one edge, and sometimes causing missing design elements along the opposite edge because of insufficient pressure being exerted on that edge. Rotation errors occur when the images on the observe and reverse dies are turned from the normal positions such as when the reverse image is at a right angle to the obverse. If no blank is between misaligned dies when they strike, the result is a clash called MAD die clash (discussed above).

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.

This broad struck Lincoln cent is the size of a nickel


Broadstrike errors are produced when the collar die (the circular die surrounding the lower die) malfunctions. The collar prevents the metal of the blank from flowing outside the confines of the die. All denominations of U.S. coins with a broadstrike will have a plain edge.

Strike through[edit]

A "struck-through" coin is made when another object comes between a blank and a die at the time of striking. That object's outline is pressed into the blank's surface. Common examples include hard objects such as staples, metal shavings, and other coins as well as soft objects such as cloth and grease. Hard objects leave sharp outlines and, on occasion, adhere to the blank producing a coin called a "retained strike-through". If the "struck-through" object is another coin, the impression left on the second coin is called brockage (discussed below). When the "struck-through" object is another coin, and that coin adheres to a die(as opposed the other coin), the adhered coin is called a "die cap" (discussed below). Two coins which adhere to one another are called "mated pairs". Softer objects, such as grease, can fill crevices in a die, producing a weak strike with a smudged appearance. These errors are often called filled dies.(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.[9])

The brockage image of the Lincoln memorial can be seen near the bottom of the coin


Full article: Brockage Brockage occurs when a mirror image of a coin is struck on a blank. After a struck coin fails to eject, a new blank is fed between the struck coin and the hammer die. The hammer die strikes the second blank leaving its image on one side while pressing the blank against the previously stuck coin which sinks its image into opposite side. Most brockages are off-center, but fully overlapping brockages are the most desirable.

Die cap

Die cap[edit]

A struck coin remains on a die and leaves its slowly fading impression (called brockage) on subsequently struck coins and, over time, changing shape to resemble a bottle cap.

Edge strike[edit]

A blank "bounces" so that it is standing on edge as it is struck producing a bent blank. Sometimes struck coins "bounce" and are struck on edge resulting in a bent coin.

Lincoln cent with second off-center strike

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".

Lincoln cent struck off-center

Off-center strike[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.[10]

Double denomination[edit]

A double denomination coin one that has been struck twice between different denomination dies such as once between nickel dies and again between quarter dies. The term is sometimes used to refer to a coin struck on the wrong planchet (see below).

Jefferson nickel struck on a one cent planchet

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. Such errors are sometimes called "double denomination" coins, but that term is also used to refer to coins struck a second time with dies of a different denomination.

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.

Matched 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.[11] 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. ^ "1955 "Bugs Bunny" Franklin Half Dollar". 2012-03-27. Retrieved 2012-04-04. 
  6. ^ "Wexler, John. (2010). "Repunched Mint Marks (RPMs) & Over Mint Marks (OMMs)." Retrieved 6 Nov. 2010". Retrieved 2012-04-04. 
  7. ^ "1945-S Micro S". 2005-01-09. Retrieved 2012-04-04. 
  8. ^ "1892-O BARBER HALF DOLLAR". Retrieved 2012-04-04. 
  9. ^ "1922 Weak D and No D Lincoln Cent Varieties". Retrieved 2013-10-25. 
  10. ^ "Lincoln Cents with Off-Center strikes". Retrieved 2013-10-25. 
  11. ^ "1979 Canadian 1-Cent Mated Set". CoinTalk. Retrieved 2014-06-15. 

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