Well I came across some info on Google about the 1971 D Kennedy Half and have to say I read where there are 1971 half dollars that might be 40% silver in them. I did weigh all my half's and one did come up 11.4 so here is my question I don't understand the tolerance info how does this work? It could go + or - right? So if I go minus then it's 11.3? Haven't a clue about this tolerance info. Here is the info I found on Google so after reading this can someone help me understand this info or what your idea is about my coin? Would appreciate your information Thank you This was posted on Coin World 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.