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Coin Errors

In any manufacturing process there are bound to be mistakes made. Both human and mechanical errors occur on an irregular basis, resulting in defective products. In most industries these bad parts are caught by quality control inspectors or by the persons responsible for packaging the finished products. When spotted, these rejects are simply destroyed. If they succeed in eluding detection, the customer who receives the erroneous part will likely return it for a refund or exchange. But what happens when the defective item is money?

The United States Mint, at its various facilities, produces billions of coins annually. This works out to more than 40 million coins daily at the Philadelphia and Denver Mints and somewhat lesser numbers at the specialized West Point and San Francisco Mints. Whenever that much of anything is produced there are bound to be errors made.

Modern coins are struck at such a high rate of speed that the human eye can barely perceive it. The fastest of the new coin presses can strike nearly ten coins per second! If these coins are somehow incorrect, the only way to spot the error is by examining the finished pieces after they fall into the receiving hopper. While this is done on an occasional basis, the day-to-day reality of producing millions of coins is that all but a very few United States coins are shipped without any visual inspection.

To help prevent error coins from leaving the mints or even from being produced in the first place, each coining facility has installed riddling devices. These are mechanical sifters that cull out undersize, oversize and mis-shapen planchets and coins. In theory, this should prevent all but normally-sized and normally-shaped coins from leaving the mint, but the evidence found in the error coins themselves proves otherwise. Though most of the errors that manage to pass through the mints’ quality control stations are of approximately normal configuration, some wildly oversize or mis-shapen pieces do escape. This is sometimes no accident, as mint employees have been caught selling error coins to collectors and dealers for a nice profit. The U. S. Mint is very aggressive about prosecuting this crime, but the high value assigned to rare error coins remains an incentive for mischief.

It was not always so. For generations, collectors of United States coins dismissed error pieces as simply curiosities, considering them to be less desirable than normally struck issues. All error coins were lumped together somewhat condescendingly under the acronym of FIDOs (Freaks, Irregulars, Defectives and Oddities). It wasn’t until the 1960s that the collecting of error coins finally gained some respect, clubs devoted to their study being established at that time. Since then, the premiums attached to error coins have risen dramatically. Concurrent with this rise in value, serious researchers have been able to determine exactly how each type of error coin is produced and, in so doing, have revealed much about the minting process in general.

Dealers and collectors of mint errors classify each piece under one of three headings: Planchet, Die or Strike. This handy “P-D-S” system is easy to remember, and it can account for just about any type of error one encounters. Of course, some coins are the product of multiple errors. For example, a defective planchet can lead to a mis-strike, with the resulting coin being the product of both “P” and “S” errors. For the most part, however, mint error coins fall under just one of the three headings. Let’s examine each one and the errors that might result from it.

A planchet is distinguished from a simple coin blank by having a raised rim. This rim is applied to the blank by an upsetting mill, which compresses the blank’s edge as it is spun between two beveled surfaces. Planchet errors encompass all mistakes resulting from a defective blank, whether or not it has passed through the upsetting mill.

The most basic type of planchet error is when the wrong planchet is fed into a press. Since both the loading tube and the die collar are sized for the appropriate denomination of coin, only planchets of the correct or smaller size can be struck within the press. This means that a dime planchet can be struck by quarter dollar dies, but a quarter dollar planchet cannot be struck by dime dies, since it won’t fit into either the feeder tube or the collar. These wrong planchet errors typically occur when a few stray planchets of one denomination remain within a hopper that is subsequently loaded with planchets for another denomination. Sometimes finished coins are still in the hopper and become overstruck with different dies.

Another planchet error, one that is highly sought by collectors, occurs when a planchet intended for a foreign nation’s coinage is struck by dies for a United States coin. This type of error was more common before 1984, when the U. S. Mint cut back its production of coins for other countries. It still may occur, however, as planchets are supplied to our mints by commercial vendors, and these vendors also service the mints of other countries. It’s not impossible for a shipment of planchets intended for one country to accidentally include those of another.

A fairly common planchet error is popularly known as a “clipped” planchet, though the more correct term is incomplete planchet. When the planchet punching press does not advance the metal strip properly, the resulting strokes may overlap previously punched out metal and produce planchets that are incomplete. Straight or irregular clips occur when planchets are punched from the peripheries of the strip. If these incomplete planchets are not caught by the riddling machine, they result in coins that are likewise missing a portion of their area.

Many other planchet errors can occur. Cents coined since 1982 are sometimes lacking their brass plating, and dimes, quarters and halves made since 1965 are occasionally struck on planchets that are missing one or both outer claddings. Conversely, they may be struck on just a clad layer that is not bonded to the copper core. Lesser planchet errors include laminated and sintered planchets, but such coins bring only minor premiums among error collectors.

The term “die error” is something of a misnomer, as anything associated with a damaged or mis-made die is more correctly described as a variety. Still, such flawed pieces are typically sought by collectors of mint errors and are described as error coins.

Perhaps the most popular die errors are major die breaks, commonly known as “cuds.” These occur when a portion of the die breaks away as the consequence of a progressive crack. Though made of tool steel, dies suffer from the repeated stress of striking planchets, and they will wear and, in some instances, crack. As these cracks deepen and reach from one edge of the die face to another, that portion defined by the crack may actually fall away from the die. The planchet metal then fills this void, the resulting coins showing a featureless blob where the die broke.

Dies may be damaged in other ways, such as having some foreign matter compressed into their surfaces. A set screw or some other part of the press falling onto a die can result in severe scarring that is then transferred to each coin. Bits of wire or fibers from a brush used to clean the die will not damage it, but they can leave impressions on a coin, since planchets are not as hard as the die face.

Striking errors are the third major class of mint errors, and these often produce the most dramatic and desirable error coins. One popular error is the multistruck coin, in which a coin fails to eject from the press and is struck again and again with multiple images. Off-centered coins are relatively common, and they occur when the planchet is not properly centered within the collar. Broadstrikes are common, and they’re the result of the collar jamming or otherwise failing to enclose the planchet. If the collar becomes jammed within the press, a partial collar error can result in which some portion of the coin’s edge is properly formed while another portion is broadstruck.

Things really get exciting when a coin adheres to the die face and then becomes a die in itself. The next few coins become brockages and will be either two-headed or two-tailed, one side showing a transposed image courtesy of the stuck coin. The piece adhering to the die will quickly become distorted, often wrapping itself around the die’s neck, forming a cap. There are numerous variations of this basic scenario, and the error coins that can result from it are often spectacular.

The collecting of mint errors is one of the fastest growing areas in United States numismatics. Several specialty clubs exist, CONECA being perhaps the most prominent. More and more American collectors are discovering the great values to be found in world coin errors, and this too is a growing field.

A broadstruck error occurs when a coin is struck without the collar to form the rim and edge that is part of the shape of the coin. Coins can be broadstruck on either Type One or Type Two planchets. When a coin is broadstruck the blank being fed into the collar will spread and distort outward as it is being struck because the collar isn't in the correct position to retain it.

Off-center coins are one of the most common and best known types of errors. This happens when a blank, as it is fed into the press, lands in the collar improperly. When this occurs only part of the blank is between the upper and lower dies. When the dies strike the blank, only that part will be struck with a design.

When a blank planchet is struck by the dies, the normal procedure is for the feeders to eject the struck coin out of the collar and into a chute. If there is a malfunction and the struck coin isn't ejected, it may receive a second or third strike by the dies. A multiple struck coin can happen in many ways and have many combinations of errors.

Mated pairs involve two individual coins with different errors that were struck together at the same time. Mated pair error combinations can be found in most error types and come in many shapes and sizes.

A brockage error can only occur when there are two coins involved. One of the coins involved will always be a struck coin which has not ejected properly. That struck coin will find its way back between the dies and will be struck next to a blank planchet which was fed into the collar. The image of that first struck coin will be impressed into that side of the blank planchet. The result will be a second coin which has images of the first coin impressed into it. Those images will be pressed into the coin and the image will be in reverse. This incuse sunken image is known as a brockage.

A capped die is caused when a struck coin sticks to the upper hammer die. Once the coin is stuck to the die face, the reverse of the struck coin becomes the new die face. When the next blank is fed into the collar and the strike occurs, the reverse design of the adhered struck coin impresses itself into the new blank. This struck coin is a brockage strike. The coin adhered to the upper die is known as a die cap. This process repeats itself as more coins are struck by the cap. The greater the number of strikes, the higher the cap metal will be pushed around the upper die shaft. Eventually, the cap brakes away from the die in the shape of a thimble.

A counterbrockage error involves a capped die and a previously struck coin. When a capped die strikes a previously struck coin, the obverse design from that struck coin will be impressed into the cap. The result will be a design where the cap face will be an incuse brockage. When a new blank is struck by this capped die with an incuse brockage image, the obverse will have a raised and spread image from that incuse design of the cap. This brockage impression is known as a counterbrockage.

An indent error occurs when two blanks are fed inadvertently into the same collar, with one blank partly overlaying on top of the other. When the hammer die strikes this combination, the upper blank will be forced into the lower blank, creating a depression which is shaped similar to the upper blank. A scarce type of indent occurs when a blank intended for one denomination lands on top of a blank from a different denomination.

Off metals and wrong planchet errors occur when a blank from one denomination is accidentally fed into a press for another denomination. Examples are a nickel struck on a cent planchet and a cent struck on a dime planchet. The coin struck on an incorrect blank will weigh exactly what the denomination of that blank would have been. An even more dramatic wrong planchet error is a coin struck on a previously struck coin of a different metal.

Bonded coins occur when the feeder system, which supplies blank planchets to the coin press, malfunctions and jams. When this occurs, a struck coin is not properly ejected and another planchet is fed into the collar and is struck. This struck coin will land on top of the previously unejected strike and crush and bond together. This may occur many times as more coins bond.

A spectacular error can be anything. Many factors have to come together for an error to be truly spectacular. An example is a SBA dollar struck on a Sacagawea dollar brass planchet. SBA dollars were struck in 1999 and Sacagawea dollars were struck in 2000. A transitional error occurs when a coin is struck on a planchet from a previous year with different metal composition. There is also a unique Sacagawea dollar struck on a SBA dollar planchet, which is also a transitional and a spectacular error.

Mule (or muling) - 1. the act of combining dies that were never meant to be together. 2. the coin that results from the inappropriate combination of two different dies.
Intentional Mule - a deliberately created mule. Examples include various Pattern issues and Restrikes made inside and outside the Mint.
Emergency Mule - a mule created out of necessity. Examples include the 1795 "Heraldic Eagle" and 1798 "Small Eagle" Half Eagle that, because of the scarcity of dies in 1798, used old, left-over reverse dies from a style that had been replaced a year (or more) earlier. Only a few examples of these exist in the U.S. series, most occurring when the Mint was in its infancy.
Error Mule - an accidental mule. Because of the high level of quality control at the Mints, this is an inherently rare class.
Double-denomination Mule - an intentional or error mule that combines dies from two different denominations. The rarest type in this class is the error mule that combines the obverse of a Washington 50 States Quarter Dollar with the reverse of a Sacajawea One Dollar (illustrated above). This is the first instance in the entire history of the United States Mints that a coin has been created with different denominations stated on each side.
Three different error mules known in American numismatics are:
The first mule is a Philippines coin, struck at the San Francisco Mint in 1918, that combines the obverse of 5 Centavos with the reverse of a 20 Centavos. The second mule is a newly discovered coin that combines the obverse of a 1999 Cent with the reverse of a Roosevelt Dime (this piece was struck on the normal Cent planchet). The third mule combines the obverse of a 50 States Washington Quarter Dollar with the reverse of a Sacajawea Dollar (all examples known were struck on the normal "golden" Sacajawea Dollar planchet).

Die Adjustment Strikes are also known as die trials. This error occurs when a coin is struck from the press with very little pressure. When the press is being set up and adjusted, extremely weak strikes occur as the strike pressure reaches its optimum level. These die trials are destroyed after being struck and are rarely found in circulation.

Proof coins are struck by technicians who hand feed the blanks into special presses. They are produced, examined, and packaged using extreme quality control. It is very unusual to find major proof errors. A few broadstrikes, off centers, double strikes in collars and off-metals have been known to be found in sealed proof sets. Proof errors are aggressively sought after by many error collectors.

A Transitional Error occurs when a coin is struck on a planchet from a previous year with different metal composition. The most famous transitional is a 1943 copper cent. This coin was struck on a 1942 copper blank, since 1943 cents were struck in steel. Other famous transitionals include 1965 coinage struck in silver instead of clad. There are also transitionals struck on blanks for the next year. An example is 1964 coinage in clad instead of silver. Most recently, transitionals were discovered involving the SBA and Sacagawea Dollars of 1999 and 2000. There are a few known 1999 SBA Dollars struck on the brass planchet for the 2000 Sacagawea Dollar. A unique specimen is known of a 2000 Sacagawea Dollar struck on a clad planchet for the 1999 SBA Dollar.

One of the most expensive, popular, and desired types of errors are the double denominations. This error happens when a coin is struck on a previously struck coin of another denomination. Examples are a cent on a struck dime, and a nickel on a struck cent. The most dramatic are those with considerable design visible from the original strike. There are a few known double denominations with different dates. The error illustrated here is a 1999 Cent on a struck Dime from 1997- 2 years apart!

The blanking press takes the coils of metal strips and punches blanks out of it, ejecting the webbing at the other end. The webbing is cut into small scrap pieces to be melted and recycled. Occasionally a scrap piece will be mixed with the blank planchets and struck by the dies. Struck fragments are rare in denominations above One Cent. The Liberty Head Nickel struck fragment illustrated here is unique for its type.

A fold-over coin is one of the most dramatic types of errors. It occurs when the blank is standing vertically between the dies. During the strike, the force is so great that it bends and folds the blank. These fold-overs can be on center or off center, and come in many different shapes. There are a few fold-overs with multiple errors, either with an additional strike or fold-over. Denominations above quarters are very scarce.

This type of error has only occurred on modern coinage. The Philadelphia Mint prepares the proof planchets which are then sent to San Francisco or West Point for striking. A few proof planchets were accidentally mixed in with the regular blanks, and struck by regular dies. Several 1999 SBA Dollars have shown up that are either broadstruck or off center on proof planchets, but struck by regular dies. These coins have extreme Prooflike fields and a pitted appearance on the unstruck portion of the blank. These are the characteristics that distinguish this rare and unusual type of mint error.

This error occurs when a planchet receives impressions from dies of two different types (designs) of the same denomination. The most spectacular example of this error is a 1970-S Proof Washington Quarter struck over a 1900 Barber Quarter (70 years apart, struck at two different mints, in the wrong metal, first for circulation, then as a Proof)! The only other example of this error is a recently discovered 2000-P Massachusetts 50 States Quarter struck over a 1999-P Georgia 50 States Quarter. While the status of the 1970-S/1900 Quarter remains questionable, we're not surprised to see the Massachusetts/Georgia error, especially in light of the spectacular mistakes made by the Mint in recent years. However, the new discovery becomes doubly exciting because production of the Georgia and Massachusetts 50 States Quarters was separated by over 70 days - the period during which the Connecticut 50 States Quarter was being produced! To accept this new dual type error, we must believe that a Georgia Quarter remained stuck in a hopper for nearly 2-1/2 months before becoming mixed with blank planchets and then struck as a Massachusetts Quarter. Fortunately, we have precedents in such coins as the 1943 Copper Cents and the many Wrong Planchet/Wrong Metal error coins to assist us with this leap of faith. According to error specialist Mike Byers, a woman spotted the new Massachusetts/Georgia error in circulation while sorting through her States Quarters. The coin changed hands several times and finally found it's way to ANACS where the coins was authenticated, certified, and graded MS-64.

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