Many of these half dollar coins were minted in .900 silver. All of the Franklin Half Dollars and the Walking Liberty Half Dollars were struck in silver. That tradition started falling off in the 1960s, the 1964 Kennedy Half dollar is 90% silver and the 1965-1970 Half dollars are 40% silver. Since 1971 however, the Kennedys minted for circulation have been struck in copper-nickel clad.