This is first article of a 2 part series:
FDR dime struck on a nail (stand in for Festivus Pole)
Over the years, I have been asked what are the differences between errors and varieties. While some errors are distinctive, some wonder why some errors are not varieties and some varieties are not classified as errors.
A basic rule of thumb is that even though errors and varieties represent changes to the basic design of the coin, they differ in how they occur and the resulting appearance of the coin.
A Mint Error is the result of an issue with the manufacturing processes causing the coin to be damaged in some way. Errors can be the result in malfunction of the equipment, imperfect coining materials, or created by human error.
Even though modern equipment is supposed the make the striking process more consistent, when the manufacturing process involves striking billions of coins, there are bound to be a few errors. Coining machines have so many moving parts and everything has to work in concern, one variation in speed, force, vibration, or tilt can make the coins look very different than intended.
Then there is the human factor. Humans are imperfect beings subject to making mistakes. Even though the machines are supposed to help guide the humans to reduce mistakes, something can go wrong, especially in an operation that involves making billions of the product.
To help understand where some of the mint errors come from, they can be categorized as three different types: Planchet Errors, Die Errors, and Strike Errors.
1943 Lincoln cent struck on a copper planchet (Courtesy of CoinTrackers)
Planchet Errors are defects of a coin that was caused by the planchet, the coin blank, being imperfect prior to the coin being struck. Planchet Errors occur prior to striking the coin but in ways that could sometimes not be detected. Types of Planchet Errors include:
clipped planchet: Term used to describe a planchet that may have been cut incorrectly from the metal sheet. The clipped area may be curved if cut into the area where another planchet was cut out or straight if cut beyond the edge of the metal strip.
delamination: A form of planchet flaw caused by imperfections in the metal whereby a thin strip of the metal separates itself from the coin.
lamination or planchet flaw: Lamination is a type of error in the planchet that occurs when a thin layer of the metal splits or peals away from the surface of the coin.
off metal or wrong planchet: A type of error that occurs when a coin is struck on a planchet that it is not normally struck, such as striking of a quarter on a planchet that was supposed to be for a nickel.
A Die Error describes a defect caused by a flaw in the dies used to strike the coin. Types of Die Errors include:
cud: The area of a coin struck by a die that has a broken area across part of its surface. The result appears as a blob of metal on the surface of the coin.
die break or die crack: Fine raised lines can appear across the coin when something causes the die to break or crack. A cracked die opens a fine line in the design allowing the flow of metal to fill in the space when struck.
filled die: A type of error that appears on a coin when a foreign substance, such as grease, fills the elements of a die used to strike coins. A filled die error can also occur when the dies are polished to remove debris during the striking process. Modern minting processes have eliminated the polishing of dies but the problems with filled dies continue.
hub doubling: Refers to the doubling of the elements on a coin that was caused by the hub being pressed more than once into a die in different angles. Hub doubling occurs prior to the striking process when the dies are created. Master hubs are pressed into the dies to create working dies for the coining process. Mistakes in this process can result in the production of many coins with the error struck into them.
mule: A mule is a type of mint error that occurs when a coin is struck with two dies that were not intended to be used together.
1955 DDO Lincoln Cent
1937-D 3-Legged Buffalo Nickel
Two of the most famous dies errors are the 1955 Double Die Obverse (DDO) Lincoln cent and the 1937-D Three-Legged Buffalo nickel. The 1955 DDO Lincoln cent and is known as the King of Errors. It is the result of hub doubling that created the double-looking lettering on the coin. It is the coin that really started the error collecting segment of the hobby.
The 1937-D Three-Legged Buffalo nickel occurred when a mint worker polished the reverse die of the Buffalo nickel too aggressively without checking his work. The result was the front-right leg of the buffalo being eliminated from the die. A few thousand were created before the Mint officials figured out they had a problem.
Off-center 50 States quarter struck in Denver
The strike occurs when the top die, usually the obverse, is pushed with such forced on a planchet sitting in a position on the anvil dies, usually the reverse, that will make the impression on the coin. Strike errors are the result of a mechanical problem that occurs during this process.
broad strike: A coin that is struck in a way that expands beyond the boundaries of the collar. A broad strike can give the coin n flat or elongated look.
brockage: A type of striking error when the coin is not ejected properly from the press and causes the mirror image of the exposed design to be struck on the next coin.
capped die: An error in which a coin gets stuck on a die and remains stuck for successive strikes. Eventually, the coin forms a “cap” on the die and imparts its image on coins it strikes. When the cap falls off, it usually resembles a small bowl.
clashed die: One of the more interesting errors occurs when during the striking process, a malfunction prevents a planchet from being in place when the dies are forced together causing them to crash into each other. This leaves the design from either side on the other. Subsequent coins are then struck with the latent image of the other side pressed into the coin.
cracked die: An error that occurs when during the stress of striking coins, the die cracks across its face. When a cracked die strikes a coin, the metal flows into the crack that impresses a raised area in the coin that is not part of the design.
filled die: A type of error that appears on a coin when a foreign substance, such as grease, fills the elements of a die used to strike coins.
incomplete strike: A coin that is missing design detail because of a problem during the striking process.
misaligned dies: A striking error caused by one or both dies not set properly in the coining machine or worked loose during striking.
multiple-struck: A type of mint error when the coin was struck more than once. A multiple-struck coin can show the design as it is struck in multiple places.
off-center strike: During the striking process, the coin is not seated in the right place in the area over the anvil (lower) die causing the coin’s design to not be properly centered on the coin.
overstrike: A type of minting error when a coin, token or medal is struck on a previously struck coin, token or medal.
partial collar strike: A type of striking error where a planchet does not enter completely into coining position and is struck partly within the collar and partly outside.
rotated dies: A type of mint error caused by the dies not being aligned when striking the coin, token or medal.
1999-P Georgia state quarter double struck and off center.
strike doubling or doubled strike: A coin that is struck more than once while in the coining machine resulting in doubling of design elements. Double strikes are different from hub doubling in that this type of error is a mechanical failure within the coining machine whereas hub doubling happens before striking. Double strike errors are rarer than hub doubling.
weak strike: refers to a coin that does not show its intended detail because of low striking pressure or improperly aligned dies.
When going to coin shows you can see some of the most fantastic errors. Some boggle the mind how they were done and how they escaped the U.S. Mint. Dealers whose concentration are errors do not reveal their secrets but I have been told that some have contacts with some of the security companies that haul money on behalf of the banks.
This topic is not complete until we talk about varieties. That will be the next post.