SKH-1c-1970D-05 Spiked Head

Description

Documented on February 15, 2017, SKH-1c-1970D-04 represents the fourth cataloged spiked head variety for the 1970-D Lincoln Memorial cent. No cross-references to other attribution systems exist for this die. The steady pace of spiked head discoveries for this date — with new varieties being cataloged across 2016 and 2017 — demonstrates how thoroughly the 1970-D cent population has been examined by variety specialists and how consistently that examination has yielded previously undocumented dies. Spiked heads arise from a specific failure mode in coin die metallurgy: the tool steel used for working dies, while extremely hard, is not immune to fatigue cracking under the cyclical loading of high-speed production. On the Lincoln obverse, the highest-relief design element is the hair detail atop the president's head, where the die steel must form the deepest recess to produce the tallest raised feature on the struck coin. This deep recess creates a stress concentration — a geometric feature where applied forces are amplified beyond the bulk average — that serves as a preferential initiation site for fatigue cracks. Once initiated, cracks follow paths of least resistance through the die's grain structure, often extending in relatively straight lines into the low-relief field area adjacent to the hair. The channel carved by the propagating crack then fills with planchet metal during each strike, producing the characteristic spike projection that gives this variety type its name.

Attribution History

• Discovered by John Smith
• Cross reference: none noted. 02/16/2017.
• Expert attribution by Cuds on Coins

External References