Ron Guth: By 1965, the rising price of silver created a situation where the instrinsic value of U.S. silver coins approached or exceeded their face value. In response, the Mint changed the composition of the Dime, Quarter Dollar, and Half Dollar from 90% silver to a clad alloy of copper-nickel outer layers over a core of pure copper.
This series includes all dates and mintmark combinations of the Washington Quarter from 1965 to 1998, minus the Bicentennial issues of 1976 and the silver Proofs from 1992 to 1998.
No rarities exist in this series. Major varieties include the Type 1 and 2 Mintmarks of Proof 1979-S and 1981-S Quarters.