Since their introduction in 1982, the copper-plated zinc planchets
used for Lincoln cents have been affected by a wide variety of plating defects.
Plating that is poorly bonded to the zinc core may blister, crack
or peel. Surface contaminants trapped between the copper plating and
zinc core can initiate subsurface corrosion, which will cause the
metal to swell and push up the copper plating in the form of small,
circular, solid mounds.
Mishaps in the plating bath can result in unplated or partly
plated planchets. Other mishaps can lead to plating that is too thin,
too thick, or oddly diffuse.
Patterns of copper deposition associated with plating mishaps are
highly variable and can assume unusual and oddly precise patterns.
Bull’s-eye patterns have appeared on a number of coins, like the
off-center cent shown here.
Various forms of prestrike damage can tear open formerly intact
copper plating, exposing the zinc core.
The foregoing is by no means a complete list of recorded plating defects.
Many countries besides the United States use zinc and steel
planchets that are plated with copper and occasionally other metals.
Not surprisingly, these planchets can suffer from the same plating
problems as domestic cents.
A highly desirable combination error is produced when a domestic
design is struck on the wrong planchet (domestic or foreign) and that
planchet simultaneously has a plating defect.
The illustrated 1998 cent was struck on a foreign planchet with
defective plating. It weighs 2.05 grams, significantly less than the
normal weight of 2.5 grams. A patch of diffuse copper plating with a
vaguely ameboid shape is seen in the center of each face. The circular
outline of the coin itself is slightly irregular.
A very similar pattern of deposition is seen on a 1997 cent that
was also struck on a foreign planchet. It weighs a mere 1.5 grams
according to Professional Coin Grading Service. As with the previous
piece, the copper plating is diffuse and is surrounded by a ring of
Because the outer ring is relatively narrow, it’s possible that
this planchet was originally completely covered by diffuse copper plating.
When the coin was struck, the expanding zinc may have simply
extruded beyond its thin copper jacket. Extrusion of the zinc core is
seen on the partly plated off-center cent that led off our discussion.
Between the years 1996 and 2000, both the Philadelphia and Denver
Mints produced Lincoln cents struck on undersized, underweight,
copper-plated zinc planchets. Weights vary but seem to fall into a
bimodal distribution, with one population averaging around 1.7 grams
and a second population averaging around 2 grams.
The lighter population also has a smaller diameter when struck. I
suspect that each population was destined for a different issue and a
different country. However, since examples of intermediate size and
weight do exist, I can’t be certain of this.
One assumes that the outside contractor responsible for providing
the U.S. Mint with copper-plated zinc cent planchets also had
contracts to produce copper-plated zinc planchets for other countries.
Sometimes the latter would get mixed in with shipments of cent
planchets, and among these unintended hitchhikers would be planchets
with defective plating.
Our last specimen is a 1992 British 10-penny piece struck on a
foreign steel planchet with a diffuse layer of copper plating.
I don’t know what country this planchet was originally intended
for, but the same can be said for the two previous domestic cent errors.
While various authorities have claimed that the foreign zinc
planchets were intended for Malaysian 1-sen and Singapore 1-cent
coins, the specifications of these two foreign denominations fail to
match the specifications of the domestic wrong planchet errors.
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