A “struck-through” error occurs when a foreign object is struck into
a coin, leaving an impression. Such errors are always more compelling
when the nature and origin of the foreign object is readily apparent.
A persistently popular category is the “struck through reeding”
error. Shown above is the reverse face of a 1971-D Kennedy half dollar
that was struck through a long piece of reeding.
dollar: The shot heard around the world in 1963, a bullet
from an assassin's weapon that ended the life of U.S. President John
F. Kennedy, is still remembered on the annually produced half dollar
struck in his honor since 1964. How much are
Kennedy half dollars worth?
Relatively little space has been devoted to the source of this
detached reeding. It’s clear that most reeding strips are derived from
previously struck coins. Since the edge of a normal coin is unlikely
to break off spontaneously, we can assume that some sort of press
malfunction or planchet defect lies behind such errors.
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Most reeding strips probably represent sheared off “fins.” A fin is a thin, vertical flange of metal that
extends from the rim/edge junction. Shown above is a modestly
developed fin on a 1984-P Washington quarter dollar. Other fins are
much larger. I’ve seen fins on cents that exceed a centimeter in height.
quarter: The Washington quarter dollar, which has been
circulating since 1932, was born out of the Treasury Department's
desire to produce a coin to mark the bicentennial of the birth of
the first president of the United States. How much
are Washington quarters worth?
Fins can be generated by excessive ram pressure (the tonnage
delivered to a planchet of normal thickness). When ram pressure is too
high, coin metal is forced into the narrow gap between die neck and
collar. Fins can also be generated by a tilted (vertically misaligned)
die. The die’s downward-tilted pole generates increased effective
striking pressure in that area. Fins are also generated when two or
more discs of coin metal are stacked on top of each other. The
increased aggregate thickness between the dies results in increased
effective striking pressure. Finally, a fin can form gradually if a
coin is struck numerous times in-collar by a die pair that has an
unusually small minimum die clearance.
Fins are easily torn when a coin is ejected. The severed fin can
remain behind in the striking chamber and get struck into the next planchet.
A 1998 5-rupee coin of India shows a reeding impression that was
probably generated by a sheared-off fin. A normal 5-rupee coin has two
bands of narrow reeding separated by a recessed security design. The
security design is pressed into the planchet’s edge during upsetting
while the reeding is generated during the strike. In this coin, the
reeding impression is significantly wider than a normal band of
reeding. This would indicate that the reeding strip was probably
derived from a coin struck so hard that the recessed security design
was obliterated while metal above and below it was extruded into a fin.
Detached reeding is also generated when the lower edge of an
expanding coin grazes the upper margin of a partially deployed collar
that is stiff but still somewhat mobile. This contact between coin and
collar can occur when an intrusive coin or planchet on the upper face
generates asymmetrically and prematurely applied striking pressure to
the coin beneath it. It can also occur in isolation, when a centered
planchet is converted into a “forced broadstrike” (Collectors’
Clearinghouse, Jan. 10, 2011). In either case, the upper edge of the
collar’s working face can shear off the lower portion of the reeded
edge to form a thin piece of detached reeding. Shown above is the
obverse face a Mexican 1-peso coin with a nearly detached section of
reeding that lies opposite a partial brockage on the reverse (upper) face.
Several less common sources of detached reeding exist. I have seen a
number of coins where part of the edge was neatly shaved off. Such
damage can occur immediately before or after the strike. The Aug. 20,
2012, column featured a double-struck 1985-P quarter dollar in which
the entire edge was shaved away after the first strike but before the
The edge of a newly-struck coin can also be sheared off if that coin
is nudged into a slightly off-center position and caught between the
hammer die and a collar frozen in the “up” position. The resulting thin, crescentic strike clip is then available
to be struck into a subsequent planchet (Collectors’ Clearinghouse,
June 15, 2015).
A last possibility would involve the edge of a brittle coin breaking away. A number of such coins
are known (Collectors’ Clearinghouse, March 14, 2011).