1971 Denver Mint Kennedy half struck in 40 percent silver
- Published: Sep 19, 2015, 11 AM
ANACS has graded and encapsulated as About Uncirculated 50 a 1971-D Kennedy half dollar that was struck on a silver-copper clad planchet instead of the intended copper-nickel clad planchet.
John Veach from Marshall’s Coin Shop in Wymore, Neb., said the coin was among circulated coins purchased over the counter.
ANACS senior numismatist Michael Fahey said graders relied on the 40 percent silver 1971-D coin’s specific gravity in making the silver-copper clad determination.
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The coin’s specific gravity is 9.5, close to the standard 9.53 for silver-copper clad, with a weight of 11.44 grams, within tolerance of the U.S. Mint standard 11.5-gram planchet.
Specific gravity for copper-nickel clad is 8.92 and a coin’s weight is 11.34 grams.
When introduced into circulation in 1964, the Kennedy half dollar’s alloy was 90 percent silver and 10 percent copper. From 1965 through 1970, a silver-copper clad composition was used. In 1970, 40 percent silver/silver-copper clad planchets were used for the production of Proof half dollars at the San Francisco Mint and Uncirculated Mint set coins at the Denver Mint. No half dollars were struck for circulation.
The silver-copper clad composition was discontinued in 1971 in favor of the copper-nickel clad composition, but returned for the collector versions of 1776–1976 Kennedy, Bicentennial half dollars.
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