Collectors of minting errors and die varieties are always on the
lookout for doubled design elements.
Well over a dozen kinds of doubling are listed in my
Comprehensive Error-Variety Checklist (at http://error-ref.com, select
“Error-Variety Checklist” from the left menu). Some, like Type II
counterclashes, are rare. Others, like minor machine doubling, are
One of the most common sources of doubling is die deterioration.
As a die pounds away at hundreds of thousands of planchets, the die
face slowly degrades. Peripheral letters and numbers become wider and
increasingly ill-defined. In some cases the margins of affected design
elements deteriorate more rapidly than the interior, leading to a form
of doubling called die deterioration doubling or DDD.
Most cases of die deterioration doubling leave a raised outline as
seen in the accompanying 1983-D Jefferson 5-cent coin. The puffy,
distorted outlines surrounding the letters of LIBERTY are
unmistakable. Nevertheless, some veteran researchers have been misled
into thinking this distortion has a different cause. I’ve seen some
cases of die deterioration doubling misidentified as “inside abraded
die doubling” and others as “outside abraded die doubling.” Inside
abraded die doubling is said to be caused by abrasives applied to the
sidewall of a design element. However, examples that have been used to
illustrate this category show classic die deterioration doubling.
Outside abraded die doubling is said to be caused by abrasives
that erode the field surrounding a design element. Examples often used
to illustrate the phenomenon — like the “poorman’s double die” 1955
Lincoln cent — are, once again, simply examples of die deterioration doubling.
Abrasion doubling — if it exists at all — is a very rare
phenomenon. Several purported examples — all on Lincoln cents — can be
found on researcher John Wexler’s website: http://
doubleddie.com/144864.html. The raised doubling seen on these
cents appears quite different from die deterioration doubling. Whether
it’s actually caused by abrasion has not been established with any
degree of certainty.
Raised die deterioration doubling isn’t always irregular.
Sometimes the raised outline is clearly demarcated with a uniform
width, as seen in the accompanying 1993-P Washington quarter dollar.
This more elegant form of die deterioration doubling is more commonly
seen in foreign coins, where breakdown of chrome plating on the die
face is thought to be the culprit.
In both of the foregoing coins, affected numbers and letters are
completely or almost completely surrounded by a raised outline. But
this isn’t always the case. Sometimes die deterioration doubling
affects only one side of a letter or number. When this happens the
doubling is sometimes mistaken for a doubled die (hub doubling). In
pre-1999 quarter dollars, the motto IN GOD WE TRUST is often the site
of this kind of asymmetrical die deterioration doubling.
Many collectors assume that die deterioration doubling is always
raised, but this is emphatically not the case. Incuse die
deterioration doubling is a well-documented phenomenon, at least in
some issues. Copper-plated zinc cents are notorious for developing
incuse die deterioration doubling. Shown here is a 1989-D Lincoln cent
with incuse die deterioration doubling affecting the date and LIBERTY.
The field surrounding these design elements is visibly swollen —
another manifestation of die deterioration.
State quarter dollars have been subject to incuse die
deterioration doubling almost from their inception. An unusually
dramatic case is seen on the reverse face of a 2007-D Idaho quarter
dollar. Many of the design elements show an incuse outline. The
outline is remarkably offset in the motto ESTO PERPETUA.
How incuse die deterioration doubling develops is not entirely
clear. It appears that the adjacent field undergoes a guided
distortion, so that the die steel bulges out alongside the affected
design elements. Perhaps the metal is conforming to a standing wave
that develops in the die face. Since the incuse doubling always lies
along the outside of the raised element on the coin, the distortion
may represent a wake forming behind the corresponding recess in the
die face as the metal flows past it.
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