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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