Struck on a 1982 mostly copper blank rather than the intended copper-plated zinc planchet
Have always checked my 1983 pennies for this condition.
The newly discovered transitional error was struck on a planchet left over from 1982 production as the U.S. Mint transitioned from bronze planchets, weighing 3.11 grams, to copper-plated zinc planchets, weighing 2.5 grams and comprising 97.5 percent zinc and 2.5 percent copper.
Source: CoinWorld
