By Mike Byers for Mint Error News ……
This unique off-metal Kennedy Half Dollar was just authenticated and certified by NGC as Struck on a Copper-Zinc Planchet, 83% Cu, 17% Zn (2.4 grams).
This is a fascinating and enigmatic mint error. No foreign coin struck by the United States Mint matches anything even close to this composition and weight. The Mint Error News website has a 69-page report of coins struck by the U.S. Mint for foreign countries. It is the most comprehensive report available anywhere. After an exhaustive search, no known planchets match the composition of this mint error.
NGC published an article discussing Mint experiments for alternatives to the existing composition of 95% copper and 5% zinc. Bronze-clad steel cents that were tested in the late 1970s were not satisfactory, so further tests were conducted during 1980 and ’81. The price of copper forced the U.S. Mint to replace the cent with an alternative composition. The final composition was 97.5% zinc and 2.5% copper. These new zinc cents were struck on January 7, 1982, at the West Point Mint. Soon thereafter, Philadelphia and then Denver struck them as well.
The weight of this Kennedy Half off-metal is within tolerance for the new 1982 cent planchet weighing 2.5g but the composition doesn’t match. Furthermore, since it does not match any composition or weight of a planchet that the United States struck for a foreign country, it likely was struck on an experimental copper-zinc planchet during 1980-1982 when the U.S. conducted tests for the new cent planchet.
The U.S. Mint used Martha Washington dies during this period to test the new copper-zinc planchets for 1982. Also, the Mint had previously conducted metallurgical testing at the Philadelphia Mint for an alternative to the pre-1943 bronze cent.
This unique off-metal Kennedy Half Dollar, likely struck on an experimental cent planchet, not only offers some insight into the U.S. Mint testing process but is also a spectacular mint error. To date, there are no Kennedy Halves known, in Mint State or Proof, that were struck on the new 2.5 gram Lincoln Cent planchet. This discovery belongs in a collection of world-class Kennedy Half mint errors or a collection of unique numismatic rarities.
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