Horizontal die misalignments occur when one die is offset relative to the opposite die. The hammer die is almost always at fault for horizontal misalignments that leave major portions of the peripheral design cut off along the coin’s edge and, it seems, for all misalignments greater than 10 percent of a coin’s diameter.
Predominance of the hammer die among major horizontal misalignments is predictable because this die is anchored within a mobile assembly that normally moves up and down but can exhibit other, unintended movements. In contrast, the neck of the anvil die is surrounded by a fixed collar, and it’s very difficult to dislodge a collar or cause one to break apart. Either situation is required to free an anvil die — a prerequisite for unwanted lateral movements.
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The hammer die is ordinarily locked into its assembly by a clamp. But any locking mechanism can come loose or break, allowing the die to shift to one side. The maximum lateral shift a hammer die can experience independently is determined by the difference between the width of the die shaft (which is embraced by the clamp) and the width of the die base.
Shown here in lateral view is a defaced cent die that widens as we move from die neck (18.94 millimeters) to die shaft (23.84 millimeters) to die base (31.66 millimeters). The maximum lateral movement can be calculated as half the difference between the two latter measurements. This would be 3.91 millimeters or a 20.5 percent misalignment. Any lateral movement greater than this would presumably cause the die to fall out of its assembly.
Limitations on lateral movement are much tighter when it comes to denominations of 25 cents and higher. These dies lack an expanded, pedestal-like base. The shaft is either straight or flares slightly as you move away from the die neck.
Despite these theoretical limitations, horizontal misalignments far larger than 20 percent are known. Shown here is a 2000-D Lincoln cent with a 29 percent misalignment of the obverse die. This die was also rotated 23 degrees clockwise. As discussed in the June 22, 2015, column, this error could also be interpreted as a pivoted die error, where the die moves around an axis of rotation located well away from the die’s center and possibly outside the die itself.
Domestic coins with horizontal misalignments of 50 percent were described in the Feb. 1, 2010, and Oct. 8, 2012, columns.
Horizontal misalignments this large would require the entire die assembly to move, as would just about any pivoted die error. Of course, even a minor misalignment could be caused by a laterally shifted die assembly.
I have not seen any domestic coin with a horizontal misalignment greater than 50 percent. I have seen images of a 5-cent coin with a weak, rotated design rim generated by a tilted, sliding die that is located at the pole opposite the one it should occupy. I estimate the misalignment to be around 77 percent. However, the design rim terminates abruptly at both ends, leaving open the possibility that it was generated by a broken die fragment trapped between the intact portion of the die and the planchet.