The Aug. 19, 2013, column introduced a novel striking error in which
a false design element is generated by a mold of stiff, smoothly
textured die fill (“grease”). I initially adopted the term
“grease-mold doubling” for this phenomenon, but it proved inadequate
for those cases in which the false element entirely replaces the true
element. So I’ve instead taken to calling the phenomenon “grease-mold
replication.” The false element itself can be termed a “replicant” or
more whimsically, a “doppelgänger,” the German word for a spectral
Having conformed to the shape of its recess, the stiff mold somehow
migrates out onto the adjacent field portion of the die. When a
planchet is fed into the striking chamber, the stiff plug of material
(presumably convex where it faces the die and concave where it faces
the planchet), acts as a micro-die that generates a raised, normally
oriented element of very low relief. The accessory element is slightly
offset from its normal counterpart and tends to be slightly enlarged
At the time of writing, the phenomenon was confined to 1995 Lincoln
cents (representing several die pairs) and restricted to the last
digit of the date. A photo of one of those cents is reproduced a the
bottom of the page. The left side of the normal 5 is visible, although
grease in the corresponding recess has left it hazy and flat. The
right side of the normal 5 was totally obscured by grease and replaced
by a false digit that is offset to the right, rotated slightly
clockwise, and is somewhat enlarged.
In recent months I’ve come across grease-mold replicants in Lincoln
cents from other years. On March 31 a collector with the username
Hogan36 posted an inquiry concerning a 1999-D cent on the Coin Community Forum. The photograph he provided
clearly shows that the right half of the last 9 of the date has been
replaced by a false numeral that is offset to the right and is larger
than the normal digit. As with other examples of grease-mold
replication, the grease has blurred or obscured other portions of the
design, most notably the IB of LIBERTY.
In early September, Larry Peterson presented a 1998 cent with
grease-mold replication on the Lincoln Cent Forum.
His example features a secondary 8 to the right of the normal 8. The
accessory numeral is slightly enlarged and is dramatically offset to
the southeast. Somewhat surprisingly, the ghostly integer invades a
portion of the field that shows no evidence of having been struck
through grease. The edge of the mold must have been neatly trimmed,
without any slop-over.
The grease-mold theory assumes the presence of a stiff mold within
which lies a shallow recess that acts as a micro-die. But if that’s
the case, I would expect to see an impression of the mold’s
surrounding wall. In other words, there should be a shallow depression
surrounding the raised number. I fail to detect any such depression in
the examples I’ve examined. It may simply be that the entire apparatus
is too thin to leave a discernible recess.
It also strikes me as odd that a raised element is generated in
every case. Ordinarily, when a plug of compacted die fill is dislodged
from its recess and struck into a planchet it generates a dropped
filling. A dropped filling impression is incuse and normally oriented
(unless it flips over or comes to rest against the opposite die). Many
dropped filling errors have been featured in Collectors’
Clearinghouse, ranging from isolated letters and numbers, to conjoined
elements, to expansive fillings involving large portions of the design.
I can only speculate that critical factors involved in grease mold
replication include the thickness, stiffness, compressibility,
resilience, and texture of the grease mold. Since the dies’ impact
generates significant heat, thermal expansion might also be a factor.
I find it significant that the incuse numeral in the die face remains
filled with grease even after the mold has migrated laterally. In
other words, the recess hasn’t been vacated, as is the case with a
dropped filling error. This suggests to me that the die fill is not
actually dislodged but that it instead swells and overflows its
recess. Whether it’s actually possible in such circumstances to
maintain the shape of the mold and the necessary stiffness to leave an
impression is unclear. But I am unable to devise an alternative mechanism.
Leaving aside the accuracy of the proposed etiology of this
phenomenon, one is vexed by associated mysteries. Why, for example,
are so few cents affected? Grease strikes involving smoothly-textured
die fill are endemic among copper-plated Lincoln cents from the very
beginning (mid-1982). The date area is affected as often as any other,
yet very few examples show grease-mold replication.
Also unexplained is why the same element is involved time after
time. What’s so special about the last digit of the date that it
should be targeted in every instance?
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