Doubling of design elements rivets the attention of error and
variety collectors. Most collectors are hoping for a doubled die (hub
doubling) or a double strike. The majority of collectors have their
hopes deflated when they find they have examples of machine doubling
and die deterioration doubling.
Many forms of doubling beyond those just mentioned can be found on
coins. Some forms are raised, some are incuse and still others are
level with the field. New forms of doubling appear regularly. Just
recently, in Collectors’ Clearinghouse in the Feb. 21 issue of
Coin World, I reported on a novel form of doubling
associated with the use of the laser-frosting technique on proof dies.
Certain forms of doubling are largely or completely restricted to
coins of particular a composition. The hardness of a metal, its
visco-elastic properties and whether it’s a solid alloy or some sort
of composite can lead to distinctive effects. This exclusivity is
readily apparent in copper-plated zinc cents.
Split-line doubling (also called split plating doubling) is the
exclusive province of zinc cents. A stellar example is shown here on a
massively expanded, strongly cupped 1999 Lincoln cent that was struck
out-of-collar (broadstruck). Lincoln’s head is surrounded by a
distorted outline of exposed zinc. Here the copper plating was
stretched to the breaking point.
Although most commonly seen on broadstrikes and off-center cents,
split-line doubling can be found in a mild form on otherwise normal
cents. It can affect any design element and is often misinterpreted as
evidence of a double strike.
Although zinc is a soft metal, it is paradoxically rough on dies.
This may be due to variable visco-elastic properties when subjected to
rapid compression under many tons of pressure. Some substances stiffen
up when rapidly deformed, in the same way that Silly Putty will tear
when rapidly pulled apart.
Unusual forms of die deterioration and die deterioration doubling
often develop on dies that strike zinc cents. The illustrated 1989-D
Lincoln cent exhibits swelling of the field on both sides of Lincoln’s
bust and the development of a low ridge (“ridge ring”) that runs
through in god we trust. The date shows a form of incuse die
deterioration doubling that is common on zinc cents but rare on other denominations.
I’ve collected a few examples of yet another type of doubling
restricted to copper-plated zinc cents. It takes the form of raised
accessory elements that extend from their normal counterparts. An
excellent example is shown on the broadstruck 2000 Lincoln cent shown
here. Puffy, raised doubling extends in a radial fashion from the
normal raised design elements on the faces of both sides.
The same sort of doubling is present on a 1993-D Lincoln cent that
was sent to me by Thomas Summers. However, this coin was struck within
the collar and is otherwise perfectly normal.
A final example, discovered by Mike Hauss on a 1993 Lincoln cent,
is shown in a photograph provided by BJ Neff. Here the doubling is
restricted to a second profile of Lincoln’s face.
These final three examples with raised doubling show no evidence
of a double strike. They’re clearly not doubled dies. Nor do they
represent a Type II counterclash (a form of die damage). The doubling
doesn’t seem to be related to die deterioration since none of the
coins show evidence of a late die state or any other signs of die deterioration.
The only possibility remaining is some form of disturbance in the
copper plating. The areas that show this raised doubling are the same
areas that often display split-line doubling. The copper plating is
highly stressed during the strike, especially at the borders of raised
design elements. Tensile stresses, compressive stresses, friction and
heat all assault the thin copper plating. This could conceivably cause
the copper plating to lift up from the underlying zinc or otherwise
alter its appearance.
I think the name “disturbed plating doubling” or “plating
disturbance doubling” would be an appropriate moniker for this phenomenon.
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