Based on the information provided, the silver content of American coins is primarily determined by their denomination and the year they were minted. A significant number of U.S. coins produced for general circulation contained silver up until the mid-1960s.
For common denominations, dimes, quarters, and half dollars minted in 1964 or earlier are composed of 90% silver. Similarly, silver dollars minted in 1935 or before also consist of 90% silver. These coins are often referred to as "junk silver," a term that relates to their silver bullion value rather than any numismatic or collectible value.
After 1964, the silver content in circulating coins was reduced or eliminated. However, certain coins produced for a limited time still contained silver, though at a lower purity. Kennedy Half Dollars minted between 1965 and 1970 contain 40% silver. Some Eisenhower Dollars, specifically those produced from 1971 to 1976, were also made with 40% silver. Another notable example is the "War Nickel," minted from 1942 to 1945, which contains 35% silver.
In addition to historical currency, the U.S. Mint produces modern bullion coins specifically for collectors and investors. These coins have a much higher purity. The American Silver Eagle, produced from 1986 to the present, and the America the Beautiful series (2010-2021) are both made of 99.9% fine silver. Special collector items, such as certain proof sets, may also contain silver versions of contemporary coins.
