SKH-1c-1991-08 Spiked Head

Description

The copper-plated zinc composition of post-1982 Lincoln cents creates distinct die interaction dynamics relevant to spiked head formation, and SKH-1c-1991-08 — reported on January 26, 2018 — was struck on planchets embodying this modern substrate. Since 1982, Lincoln cents have been produced on a 97.5% zinc core with a thin 2.5% copper plating, replacing the 95% copper alloy used from 1962 through 1982 and the earlier bronze composition. Zinc is softer than copper, and the thin copper plating adds minimal structural reinforcement, meaning the planchets deform more readily under striking pressure than their bronze predecessors. This increased malleability allows planchet metal to flow more aggressively into die cracks during striking, potentially producing more prominent spikes from the same-sized crack than would form on a harder bronze planchet. The zinc composition also creates different thermal transfer characteristics between the planchet and die during striking, altering the pattern of heat-induced stress that contributes to die crack initiation. These compositional factors may partially explain why spiked heads appear with notable frequency on zinc-era Lincoln cents compared to earlier bronze issues. Struck at Philadelphia on copper-plated zinc planchets composed of 97.5% zinc and 2.5% copper, weighing 2.5 grams and measuring 19mm.

Attribution History

• Discovered by Steve Siegfried
• Cross reference: none. 01/26/2018.
• Expert attribution by Cuds on Coins

External References