The time period from 1960-1969 saw some significant changes for the Proof Sets issued by the United States Mint. Sales continued to grow from 1960 to 1964 to nearly 4 million sets. Following this peak was a suspension of traditional proof sets for three years, coinciding with a compositional change. When proof sets resumed, the packaging and production Mint were changed.
The decade began with the 1960 Proof Set. This set had a mintage of about 1.7 million. The mintage took a big jump in the following year to exceed the 3 million mark. The peak mintage was reached in 1964 when 3,950,762 sets were produced. This remained the highest total until the Bicentennial Proof Set issued in 1976.
The Proof Sets of the decade underwent a significant compositional change. Until 1964, the half dollar, quarter, and dime were all struck in 90% silver. When the composition changed in 1965, proof set issuance was suspended and Special Mint Sets were issued in their place until 1967. When Proof Sets resumed in 1968, the quarter and dime were struck in a copper nickel clad composition and the half dollar was struck in 40% silver.
Another important change that occured after the short suspension of proof sets was the producint Mint. Up until 1964, modern proof sets had been produced at the Philadelphia Mint. From 1968 onwards, the San Francisco Mint took over the duties of proof coinage production for the annual proof sets. The sets packaging also underwent a change from the flat packs, to a rigid plastic lens which contained the coins.
