Several kinds of alignment errors are known to affect coining dies and die assemblies. In a rotated die error a die spins a round a central axis. A horizontal misalignment entails a die or die assembly shifting sideways. A vertical misalignment (tilted die error) occurs when a die or die assembly leans away from the vertical.
Major vertical and horizontal misalignments are generally restricted to the hammer die, as its movements are unconstrained by the collar.
Sometimes a die will experience two simultaneous alignment errors. I’ve previously noted the frequent and entirely predictable pairing of a severe vertical misalignment with a horizontal misalignment. Less predictable is the co-occurrence of a horizontal misalignment with a rotated die error.
Some of the latter may actually represent a fourth alignment error — a pivoted die error. As the name implies, this involves a die assembly pivoting around an axis removed from the die’s center and possibly located outside the striking chamber. The path taken by the die describes an arc.
Since the term “horizontal misalignment” has traditionally been restricted to purely translational (sideways) die movements, I will use the nonspecific term “horizontal shift” when the nature of the alignment error is unclear. For similar reasons I’ve opted to use the term “angular displacement” when referring to what may be either a rotation or a pivot.
Depending on where the pivot point is located, there will be a fixed relationship between horizontal shift and angular displacement. For example, if we place the pivot point on the rim at 12:00, a 37.5 percent horizontal shift will be associated with a 45 degree angular displacement. If the angular displacement remains constant, the horizontal shift will increase proportionally as the pivot point grows more distant. For example, if we maintain a 45 degree angular displacement but double the distance of the pivot point to twice the coin’s radius, the horizontal shift will have doubled to 75 percent.
Our first potential pivoted die error is a broadstruck 2000-D Lincoln cent in which the obverse (hammer) die shows a horizontal shift of 29 percent and a clockwise angular displacement of 23 degrees.
Our second candidate is a double-struck 1983 Jefferson 5-cent coin in which the first strike was normal and the second quite weak. The second strike shows a 26 percent horizontal shift coupled with a 25 degree clockwise angular displacement.
In both cases, these measurements are compatible with a pivoted die error, a horizontally misaligned and rotated die, or a devilishly complex combination of all three alignment errors.
Certain die clashes provide indirect and equally inconclusive evidence of pivoted die errors. Over three dozen “radically misaligned” die clashes are known from Lincoln cents minted between 1990 and 2000 (www.maddieclashes.com). The vast majority were produced by the light impact of an obverse (hammer) die that was tilted and horizontally misaligned to a remarkable degree (some over 50 percent). But a few, like MDC-1c-1996-01, can be interpreted as pivoted die clashes.