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 incredibly common.
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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