Enigmatic die defect may be a recurring die subsidence error

Collectors' Clearinghouse column from March 31, 2014, issue of Coin World
By , Special to Coin World
Published : 03/14/14
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For almost as long as I’ve been collecting error coins I’ve been running across 1973-D Lincoln cents with a peculiar die defect on the reverse face. 

As shown in the accompanying photos, a low ridge runs through the left side of the Lincoln Memorial, generally passing through the second and third bays. Other parts of the memorial may be affected. 

The ridge can be slightly farther to the left, running instead through the first and second bays. A bulge may appear below the base of the memorial, in line with the third bay or the fourth column. The upper portions of the second or third column may show modest to severe narrowing. Above the colonnade, many examples show interruptions or distortion of the frieze, cornice and attic.

A description applicable to all examples is impossible because of the significant variability that exists within the general pattern. Such variability is not entirely surprising because the defect is associated with many different dies. The eight examples consulted for this column were struck by six different die pairs.

When these coins appear for sale, the defect is usually said to result from clashed dies. It’s true that the ridge’s location and oblique path almost line up with the back of Lincoln’s coat. However, the ridge is slightly to the left of where it should be and nothing else about it resembles a clash mark. The ridge is too broad, too elevated, too irregular and too ill-defined. No other clash marks ever accompany the ridge. Finally, clashed die errors are not known to cause distortion or loss of significant portions of the design.

Since the defect occurs on many reverse dies, it’s possible that we’re dealing with deformation of a master die or a working hub. If so, we would have to be looking at a case of progressive deformation to accommodate all the variability. However, this hypothesis fails when you look at the pattern of variability in detail. Deformation spreads and worsens; it doesn’t change position or reverse its severity. On some examples the bays are significantly deformed but the roof is intact. In other examples, the roof is badly affected but the colonnade modestly so.

I can only surmise that this is a recurring die subsidence or soft die error (the two error types are closely related and can converge in appearance). While die deformation errors of this sort are usually restricted to a single die, they will sometimes affect multiple dies when there is a fundamental flaw in the die steel or when there is a repeated misstep in die preparation (annealing, tempering, quenching).

One precedent can be found in the April 4, 2011, column wherein I describe two 1988-P Jefferson 5-cent coins that were struck by different dies but that nevertheless show nearly identical bulges at the top of Jefferson’s head (shown).

The appearance of a highly localized and very distinctive-looking zone of subsidence in the same area on multiple dies is difficult to explain. This is especially true when the defect is neither centrally located nor located along the coin’s perimeter.

It’s possible that the rod of die steel had a long, asymmetrically positioned imperfection that ran the length of the rod, rather like a long strip of tuna embedded within and running along the length of a sushi roll. Slice through the rod and the imperfection will appear in the same spot. But once a stubby cylinder of die steel has been cut off, the position of the defect will be random with respect to the design that’s eventually hubbed into the working die. That is, unless a positional guide mark was engraved into the rod of die steel before it was sliced into usable segments. But as far as I know, “flats” are ground into the shank of the die well after it is cut from the rod of die steel.

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