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
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:
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
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
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
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
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
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 STRUCK COINS
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.
DOUBLE- AND MULTIPLE-STRUCK
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.
WRONG METAL / WRONG
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
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
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
DIE ADJUSTMENT STRIKE
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.
DOUBLE DENOMINATION ERRORS
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.
ERRORS ON PROOF PLANCHETS
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
DUAL TYPE 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.