The U.S. coins that contain the most silver are Roosevelt and Mercury Dimes, Washington Quarters, and Walking Liberty, Franklin and Kennedy Half Dollars minted in 1964 and earlier, according to American Rare Coins and Collectibles. These coins contain about 90 percent silver.
Uncirculated Roosevelt Dimes from 1946 through 1964 are more valuable than circulated ones. Collectors should not bother sorting their circulated Roosevelt Dimes by date, according to American Rare Coins and Collectibles. Some Mercury Dimes, also known as Winged Liberties, are worth a substantial premium. Even in low-grade condition, the most valuable Mercury Dimes are uncirculated or nearly uncirculated dimes minted between 1916 and 1931, especially the 1916-D, 1921 and 1921-D dimes.
Circulated Washington Quarters from 1932 through 1964 are worth the value of their silver content. Uncirculated Washington Quarters from this era are worth more. The key dates to look for are 1932-D and 1932-S. Kennedy Half Dollars only contained 90 percent silver in 1964. Circulated coins are worth the value of their silver content, but rolls of uncirculated coins may be worth slightly more. Uncirculated Walking Liberty Half Dollars from 1916 through 1947 and Franklin Half Dollars from 1948 through 1963 are valuable. Certain dates of uncirculated Walking Liberty Half Dollars are also worth a high premium.