For the first year of issue in 1964, the Kennedy Half Dollar was struck in a composition of 90% silver and 10% copper. The coins had a standard weight of 12.50 grams with a diameter of 30.6 mm and a reeded edge.
From 1965 to 1970, a new composition was adopted with reduced silver content. The coins consisted of an outer layer of 80% silver and 20% copper bonded to an inner core of 20.9% silver and 79.1% copper. This yielded a net composition of 40% silver and 60% copper, with the coins carrying a weight of 11.50 grams.
Starting in 1971, the silver content was removed completely from the half dollar denomination. The coins consisted of an outer layer of 75% copper and 25% nickel bonded to an inner core of pure copper. This yielded a net composition of 91.67% copper and 8.33% nickel, with the coins carrying a weight of 11.34 grams. Over the years, certain numismatic issues of the series have utilized the previous 40% silver or 90% silver compositions.
Kennedy Half Dollars have been struck at the Philadelphia and Denver Mints for circulation and at the San Francisco Mint in proof format. The mintmark for the 1964 Denver issue is found on the reverse, below the right claw of the eagle. From 1968 to present, the mintmark is found on the obverse, beneath the truncation of the neck. The coins struck in Philadelphia did not carry a mint mark for the initial years of the series, but began using the “P” mint mark in 1980.