US Coins

Collectors' Clearinghouse impact-induced die deformation

Reciprocal die deformation is a rare phenomenon in which one die face sinks in while the other bulges out in a complementary fashion. 

Until recently, I knew of only one die pair afflicted in this manner. It produced a large group of 2001-P Kennedy half dollars, one of which is shown here. The central two-thirds of the reverse die sank in while the central portion of the obverse die bulged out less impressively, producing coins with a convex/concave cross-sectional profile (Collectors’ Clearinghouse, Sept. 16, 2013).

I recently came across a very different case of reciprocal die deformation in an off-center 2007 India 2-rupee coin minted at the Calcutta facility. Here deformation affects about 180 degrees of each die’s perimeter.

On the left side of the obverse face, a deep and profoundly irregular collar scar runs through the unstruck portion of the planchet. The collar scar serves to identify the obverse die as the anvil die (the usual setup for recent Indian coins). Just to the right of the collar scar, the obverse field and its contained design elements slope upward to meet the unstruck crescent.

Normal Indian 2-rupee coins of this design display a nearly flat peripheral field, so the exaggerated curvature seen on this coin is quite abnormal. The left side of the obverse die (bearing the denomination and the Ashoka lion) retreated or was pushed in, leaving the die with a convex cross-sectional profile in this area. The coin itself therefore has a correspondingly concave cross-sectional profile in this same area.

Let’s now turn to the right side of the reverse face, which was struck by the hammer die. Indian coins are struck in medal rotation, which means that both obverse and reverse designs point in the same cardinal direction. Because of this orientation, the left side of the obverse face and the right side of the reverse face lie directly across from each other in vertical space.

On the right side, the perimeter of the reverse field, along with its contained elements, exhibits a conspicuous downward curvature, which means that the die face itself was concave in this area. It may be that the greater portion of the die face sank in, leaving only a crescent on the right side occupying the original horizontal plane of the die face. However, since there’s no sign of deformation in the coin’s interior, I think it’s more likely that the periphery of the die protruded beyond the original horizontal plane. In cross-section, this portion of the die face would have resembled the inside of a contact lens. The inflected edge of the die face was rather sharp, and sliced deeply into the planchet.

Elsewhere on the coin we find evidence of a major press calamity. The coin’s obverse field is more laterally positioned than the reverse field, leaving the unstruck portion of the planchet wider on the obverse face. This suggests that the anvil die and its surrounding collar were horizontally misaligned. This rare alignment error can only occur if the collar breaks free of its moorings or breaks apart, freeing the anvil die from its confinement. The terribly ragged collar scar is consistent with such an error as it indicates that the collar was seriously damaged.

I suspect that a massive impact from the side drove the collar into the anvil die neck, causing downwarping along the left side of that die face. This same impact may have forced the right side of the hammer die to protrude, provided that the hammer die was at the lowest point of its downstroke (and therefore within the collar). It seems less likely that the hammer die was damaged while situated above the collar. A final possibility is that the hammer die escaped the impact but instead conformed quickly to the deformation already present on the anvil die through the medium of the relatively large (26.75 millimeters), relatively thin (5.8 grams), stainless steel 2-rupee planchets. This curious scenario would probably hinge on the dies being softer than normal.

This may indeed have been the case. One would think that die steel would shatter before it would undergo the sort of drastic deformation seen here. The fact that the dies didn’t shatter suggests that the die steel was unusually malleable and that this set the stage for the subsequent, impact-induced distortion. 

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