Any United States dime, quarter, half dollar or dollar that is dated 1964 or earlier is made of 90% silver. In the dime series, all coins dated 1965 or later are clad coins and contain no silver at all. Quarters dated 1965 or later are all copper-nickel clad coins except for the dual-dated Bicentennial Quarters that were sold by the Mint in special Mint Sets and Proof Sets. These quarters contain 40% fine silver and have an "S" mint mark. They are different from the Bicentennial quarters you can find in circulation and were sold by the Mint at a premium to collectors.
In the Kennedy Half Dollar series, the 1964 of course is 90% silver. Halves dated 1965 through 1970 contain 40% silver. Halves dated 1971 or later are copper-nickel clad coins with the exception again of the special Bicentennial halves sold in the Mint Sets and Proof Sets with the "S" mint mark, which are 40% silver. Among Eisenhower dollars, coins dated from 1971 through 1974 with the S mintmark are 40% silver. In addition, the special Bicentennial Sets contained 40% silver coins. All other Eisenhower dollars are copper-nickel clad coins.