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Planchet Errors
Alloy errors: All U.S. coins are produced from
alloyed metals, mixed when molten to strict specifications. If mixed incorrectly, the
metals may cool in non-homogeneous form, with streaks of different metals appearing on the
surface of the coin.
Damaged planchet |
Damaged planchets: Planchets are subject to various
sorts of damage, including cracks (not to be confused with die cracks), holes and major
breaks. (A planchet is an unstruck disc of metal that when struck between coining dies,
becomes a coin.)
Fragment
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Fragments, scrap struck: Small pieces of coinage
metal - fragments and scrap left over from the blanking process - sometimes fall between
the dies and are struck. Fragments must be struck on both sides and weigh less than 25
percent of a normal coin's weight to qualify as a struck fragment. Planchet scrap is
generally larger than a fragment, and usually has straight or curved edges as a result of
the blanking process.
Incomplete planchet
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Incomplete planchets: Often, though erroneously,
called a "clip," an incomplete planchet results from a mishap in the blanking
process. If the planchet strip does not advance far enough after a bank of punches rams
through the metal, producing planchets, the punches come down and overlap the holes where
the planchets were already punched out. Where the overlapping takes place, there is a
curved area that appears to be "missing" from the planchet. If the strip slides
to the side too far and the punches overlap the side of the strip, the missing area is
straight. If the punches overlap the end of the strip, the missing area is either ragged
or straight, depending on whether the end of the strip was trimmed.
The word "clip," commonly used, suggests a piece of the planchet was cut off,
which is not the cause of the incomplete planchet. "Clip," when properly used,
refers to the ancient process of cutting small pieces of metal from the edges of precious
metal coins for the bullion; that is why U.S. gold and silver coins have lettered or
reeded edges, to make it more difficult to clip a coin.
An "incomplete planchet planchet" occurs when the punch does not completely
punch out a planchet, but leaves a circular groove. If the strip advances improperly,
planchets overlapping the incomplete punch will bear a curved groove; the groove remains
visible after the coin is struck.
Many incomplete planchet errors have a "signature" known as the Blakesley
effect. The area of the rim 180 degrees opposite the "clip" is weak or
non-existent since the rim-making process in the upset mill is negated by the
"clip." The lack of pressure in the upset mill at the clip results in improper
formation of the rim on the opposite side.
Lamination
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Laminations: During the preparation of the planchet
strip, foreign materials - grease, dirt, oil, slag or gas - may become trapped just below
the surface of the metal. Coins struck from this strip later may begin to flake and peel
since adhesion is poor in the location of the trapped material. The Jefferson, Wartime
5-cent pieces are particularly susceptible to lamination, due to the poor mixing qualities
of the metals used during the war metal emergency.
Split planchet (split before striking) |
Split planchets: Planchets can split due to deep
internal laminations, or in the case of clad coinage, because of poor adhesion of the
copper-nickel outer layers to the copper core. Planchets may split before or after
striking. Those splitting before generally exhibit weak details due to lack of metal to
fill the dies, while those split afterwards usually depict full detailing.
On non-clad coins, the inner portion of the split shows parallel striations typical of
the interior structure of coinage metal.
Thick and thin planchets: Planchets of the wrong
thickness are produced from strip that was not rolled properly. Too little pressure can
result in planchet stock that is too thick; too much pressure can result in a thin
planchet. If the rollers are out of alignment on one side, a tapered planchet - thicker on
one side than the other - is created.
Unplated planchets: New in U.S. coinage, unplated
planchets became possible in 1982 with the introduction of the copper-plated zinc cent
(and briefly in 1943 with the zinc-coated steel cents). The zinc-copper alloy planchets
are plated after they are punched from the strip but some planchets miss the plating
process. Coins struck on the unplated planchets are grayish-white in color. Beware of
cents which have had their plating removed after leaving the Mint. Although beyond the
ability of a novice collector to detect, any of the authentication services currently
operating should be able to distinguish between a genuine piece and an altered version.
Wrong planchet
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Wrong metal, planchet, stock: A wrong metal error
is struck on a planchet intended for a denomination of a different composition. This
includes 5-cent coins struck on cent planchets, cents on dime planchets, and higher
denominations struck on cent and 5-cent planchets.
A second type is the wrong planchet error, defined as a coin struck on a planchet of
the correct composition, but the wrong denomination. These include quarter dollars struck
on dime planchets, half dollars struck on quarter dollar and dime planchets, and dollars
struck on other clad planchets.
Some specialists claim that wrong metal and wrong planchet errors are striking errors,
not planchet errors. Their argument? The planchet is OK. It was just fed into the wrong
coining press.
Wrong stock |
A third type is the wrong planchet stock error. It occurs when clad coinage strip
rolled to the thickness of one denomination is fed into the blanking press of another
denomination; the diameter is correct, but the thickness is thicker or thinner than
normal. The most common appears to be quarter dollars struck on planchet stock intended
for dimes.
Double denomination |
A fourth, rarer form is the double denomination. It occurs when a coin is struck on a
previously struck coin, such as a cent struck over a dime. Since the U.S. Mint has struck
coins for foreign governments in the past, it has been possible to find in circulation
U.S. coins struck on planchets intended for foreign coins, as well as U.S. coins struck on
previously struck foreign coins.
Another rare type of wrong metal error is called the transitional error. It occurs as
the composition of a coin changes. Some 1965 coins are known to be struck on silver
planchets of 1964 composition, while some 1964 coins were struck on clad planchets (1964
coins were struck through 1965, with planchets for both types of coins available side by
side).
One fact true for all errors of this broad category is that the planchets must be of an
equal size or smaller than the intended planchet. A 5-cent planchet, for example, would
not fit between the dies of the smaller cent.
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