The provided context from Wikipedia and the U.S. Mint is insufficient to answer the question regarding the composition of the half dollar. The following answer is therefore based on established numismatic and historical information.
The metallic composition of the United States half dollar has undergone significant changes throughout its history, primarily driven by the fluctuating value of precious metals. From its inception in 1794 until 1964, the half dollar was composed predominantly of silver. The standard for most of this period was an alloy of 90 percent silver and 10 percent copper, a composition established to ensure the coin's intrinsic value was close to its face value.
A major shift occurred with the passage of the Coinage Act of 1965. In response to rising silver prices, the composition of the Kennedy half dollar was altered for coins minted between 1965 and 1970. These coins were produced with a clad structure, featuring outer layers of 80 percent silver and 20 percent copper bonded to an inner core of approximately 21 percent silver and 79 percent copper. This resulted in a coin with an overall composition of 40 percent silver.
Beginning in 1971, silver was entirely eliminated from circulating half dollars. Since that time, all standard circulation-issue half dollars have been made with a clad composition identical to that of the dime and quarter. This consists of outer layers of 75 percent copper and 25 percent nickel bonded to a core of pure copper. While the U.S. Mint has continued to produce special collector versions and proof sets containing 90 percent or 99.9 percent silver, the standard half dollar intended for circulation is a copper-nickel clad coin.
