Variety and Error Coins

Note: This page was written to provide a brief introduction to error coins and variety coins as background material for future posts. It is not intended to provide an exhaustive list of the different types of error coins and variety coins.

The United States Mint inspects coins during production to prevent minting mistakes from reaching the public, but some still slip through. Collecting such mistakes came into favor in the 1950s, partly due to the widely publicized 1955 Doubled Die Obverse Lincoln Cent. Collecting exploded after third-party grading services began categorizing and identifying them as part of their grading services. Because the United States Mint strives to prevent the release of these coins, collectors focus not on how many were struck, but how many were released.

As this area of coin collecting evolved, minting mistakes were divided into error coins and variety coins. Error coins result from mistakes in the coin production process and are generally unique and unpredictable. Variety coins (or “die variety coins” to be precise) result from variations in the dies used to strike the coin. All variety coins struck with the same obverse/reverse die pair will have the same variations.

Die errors can cause some confusion as they fall into both of the above definitions. Die errors, such as die cracks and die breaks, are faults in a die that occur during production. The American Numismatic Association classifies the resulting coins as error coins. If the error is not fatal to the die and the United States Mint continues to use the die despite the fault, the resulting coins will have the same characteristics as other coins and are commonly referred to as variety coins.

The Coin Production Process

To understand error coins and variety coins, a basic understanding of the coin production process is required.

Working Hubs and Dies. To create the dies used in coin production, the artist’s design is mechanically engraved onto a master hub. A hub is a hardened steel cylinder with a positive, raised relief of a coin’s design. The master hub is used to make master dies. A die is a hardened steel cylinder with a negative relief of a coin’s design. Because the United States Mint uses thousands of dies each year, the master dies are not used to strike coins. The master dies are used to create working hubs, which in turn are used to create working dies. A complete description of this process can be found on the United States Mint’s website here.

Note: The reference above to positive and negative reliefs on hubs and dies is not accurate for incuse-designed coins, of which the United States Mint has minted two – the $5 Gold Indian Half Eagle and the $2½ Gold Indian Quarter Eagle.

Mint Marks. Before 1985, for proof and commemorative coins, and 1991, for circulating coins, mint marks were hand-punched. After that, mint marks were incorporated into the coin’s design.

Production. Blanks, flat metal discs that will eventually become coins, are punched from long metal coils specifically created to a coin’s specifications. The blanks are annealed (heated to high temperatures in an oxygen-free environment) to soften the metal, so they will hold the design better when struck. The blanks are then washed in a solution containing cleaning and anti-tarnish agents to restore the blanks to their original color. The blanks are next fed into the upsetting mill, which creates a raised rim on the blanks to protect the design and make the coins stackable. A blank with a rim is called a planchet. The planchet is placed into a collar and struck with the obverse and reverse dies. The collar is effectively a third die that forms the edge design and prevents the planchet from expanding during striking. Some coins, such as modern small dollars, have an additional step in which the edge lettering is punched onto the coin. The coins are then inspected, bagged, and sent to the Federal Reserve Banks for distribution. A more detailed description of this process can be found on the United States Mint’s website here.

Error Coins

Error coins result from errors in the coin production process and are generally unique and not amenable to series or type set collections. They can fall into one of four categories, depending on where the error was introduced: planchet errors, die errors, striking errors, and post-striking errors. The types of errors that fall into these categories are numerous, and a few examples are provided here. This is not an exhaustive list of the types error coins.

Planchet Errors – Errors in the Creation of the Planchet

Alloy Mixing. Improperly mixed alloys, the presence of other trace metals, or incorrect metal percentages can lead to planchet streaking, cracking, or crystallization.

Damaged Planchets. After pouring the metal, additional problems in the planchet can occur, such as gas bubbles or improper annealing.

Incomplete Planchets. Punched blanks can be incomplete if the metal sheet does not advance properly in the blanking press or if punched from the end of the metal sheet.

Split or Missing Clad Layer. Many modern coins have an inner layer of one alloy and outer layers of another alloy. Error coins can result if one of those outer layers is missing or split from the inner layer.

Die Errors – Errors Due to Work, Damaged, and Repaired Dies

Working dies are used to mass-produce coins under immense pressure. Dies wear over time; cracks form and worsen; the design chips away; and faults are introduced during repair.

Die, Hub, and Collar Cracks. Die cracks on a die will appear as raised lines on the struck coin. Die cracks on a hub will appear as a raised line on the struck die and an incused line on the struck coin.

Die, Hub, and Collar Chips and Breaks. Die chips occur when part of the design is chipped away, and a blob of metal forms in that area instead. When a large portion of the design is involved, the fault is referred to as a die break rather than a die chip. When a complete section of the die falls off, most of the metal flows into that area, creating a large blob of metal, called a cud, and a weakened design on the remaining part of the struck coin.

Worn, Damaged, and Clashed Dies. As dies wear over time, the design can become faded. Eventually, the constant striking of planchets can transfer a portion of the design to the opposing die, leaving a ghost image on the struck coin. If the dies attempt to strike a coin when a planchet is not present, the dies clash, and a greater portion of the design can transfer to the opposing die. Dies can become damaged in other ways. For example, a die might be gouged if struck with a hard object.

Die Repair Errors. As dies become damaged, attempts are made to repair them and extend their life. Abraded dies are where abrasives are used to repair the die’s surface or remove clash and gouge marks, but leave scratch marks in their stead. Re-engraved dies are those in which portions of the lettering are re-engraved. The 1937 Three Legged Buffalo is a famous example of a die repair error where the die was overpolished to remove clash marks and the front right leg of the Bison was inadvertantly erased.

Striking Errors – Errors That Occur When a Coin is Struck

Incorrect Planchets. Incorrect planchets or even something other than a planchet can find its way into the striking chamber. The 1943 Bronze Lincoln Cent was the result of a planchet from the prior year reaching its way to the striking chamber. Sometimes a planchet of the wrong denomination finds its way to the striking chamber.

Abnormal Objects. Other objects in addition to the correct planchet can find their way into the striking chamber. For example, dies were cleaned with wire brushes, and the bristles from those brushes have been found pressed into the coin.

Double Strikes. Stuck coins that fail to be ejected from the striking chamber can be struck a second time, doubling the design. Off-center double strikes can occur where the coin is partially ejected from the striking chamber.

Misaligned Dies. Offset die strikes occur where the obverse and reverse dies are not completely aligned. Rotated die strikes occur where the rotation of the obverse and reverse dies is not in “coin alignment.” Coin alignment is when the top of the obverse aligns with the bottom of the reverse.

Post-Striking Errors – Edge Lettering

Edge lettering is found on some eighteenth-century coinage, as well as on modern Presidential Dollars and American Innovation Dollars. For uncirculated modern dollars, after the coin is struck, it is fed into an edge lettering machine, and the orientation and rotation of the lettering is random. A coin can bypass the machine altogether (missing edge lettering), pass through the machine more than once (double edge lettering), or suffer from a weak strike (weak edge lettering). Grading services designate edge letting as Position A (upright edge lettering when the obverse faces up) or Position B (upright edge lettering when the reverse faces up). For proof coins, the edge lettering is integrated into the striking process with the use of a special collar, and the edge lettering should have the same orientation and rotation on all coins.

Die Variety Coins.

The variety of coins results from variations in the die pair used to strike a coin. All coins struck with the die pair will have the same variations. They can fall into one of four categories, depending on how the error was introduced: intentional design varieties, mint mark varieties, doubled die varieties, and die state varieties.

Intentional Design Changes.

For intentional changes in a design, the difference between a design type and a design variety is generally a question of the scale of the change. Significant changes, such as the Buffalo Nickel Type 1, “FIVE CENTS” raised, and the Buffalo Nickel Type 2, “FIVE CENTS” in Recess, are designated as different design types. Minor changes, such as the large and small dates on the 1982 Lincoln Cent, are designated as varieties of the same design type. The dividing line between the two designations is sometimes blurred, and, to the dismay of type set collectors, industry experts do not always agree on which side a particular coin falls.

Mint Mark Varieties

Mint mark varieties result from stylistic differences in the punch, the placement of the mint mark, or the manner in which it was punched. Such varieties no longer occur now that the mint mark is part of the coin’s design. However, a doubled-die coin variety (discussed below) affecting the mint mark has become possible because of this change.

Stylistic Differences in Mint Marks. The 1979 Type 1 and Type 2 San Francisco Mint Mark, found on all denominations of proof coins, is a modern example of mint-mark varieties due to stylistic differences.

The Placement of the Mint Mark. There are only four known mint mark placements on the 1909-S VDB Lincoln Cent, and experts use this knowledge to detect counterfeits.

The Punching of the Mint Mark. Hand-punched mint marks require multiple strikes. A repunched mint mark is a mint mark in which these punches are not aligned, creating multiple impressions of the same mint mark on the working die. Sometimes a working die would be transferred to another branch. An over mint mark is where a different mint mark is punched over the initial mint mark.

Note: Prior to the mid-nineteenth century, dates were also punched onto working dies, and similar types of varieties in early coins can be found with respect to punched dates.

Doubled Die Varieties

Multiple strikes of a working hub are needed to create a working die. A doubled die variety results from the later strike being misaligned, and some of the design elements on the working die are duplicated. All coins struck from that die will appear duplicated. Doubled die obverse (DDO) coins are varieties where the obverse of the coin is doubled, and doubled die reverse (DDR) coins are varieties where the reverse of the coin is doubled.

Die State Varieties.

Working dies, used to mass-produce coins, wear over time. At the beginning of the coin’s life, the design struck on the coin appears sharp and detailed. By the end of the die’s life, it becomes worn, and the design appears washed out. When a particular die can be identified by die markers (i.e., variety coins), die progression varieties follow the life of that die over time. Die state varieties refer to progression varieties at the beginning, middle, and end of the die’s life.

References

American Numismatic Association. (n.d.) Course 4. The Modern Minting Process
& U.S. Minting Errors and Varieties. https://www.money.org/diploma-program.

CoinWeek. (January 7, 2026.) The 1955 Doubled Die Lincoln Cent: America’s Most Famous Coin Mistake. https://coinweek.com/the-1955-doubled-die-lincoln-cent-americas-most-famous-coin-mistake.

Lange, David W. (May 1, 2004). Numismatic Guarantee Company. A Look at Mintmarks: Part One. https://www.ngccoin.com/news/article/682.

Lange, David W. (June 1, 2004). Numismatic Guarantee Company. A Look at Mintmarks: Part Two. https://www.ngccoin.com/news/article/678/

McMorrow-Hernandez, Joshua. (March 3, 2025.) The 1955 Doubled Die Lincoln Cent Turns 70. Professional Coin Grading Service. https://www.pcgs.com/news/the-1955-doubled-die-lincoln-cent-turns-70

McPike, Sharron. (February 4, 2015.) Behind the Scenes at the Denver and San Francisco Mints. https://www.usmint.gov/news/inside-the-mint/behind-the-scenes-at-the-denver-and-san-francisco-mints.

Meredith, Stephanie. (April 2021.) Coin Production. United States Mint. https://www.usmint.gov/learn/production-process/coin-production

Meredith, Stephanie. (April 2021.) Die Making at the U.S. Mint. United States Mint. https://www.usmint.gov/learn/production-process/die-making.

Numismatic Guarantee Corporation. (n.d.) What is a Variety? https://www.ngccoin.com/variety-plus/what-is-a-variety.