1964 Kennedy Half Dollar : The 1964 half dollar, made of 90% silver, is often the most valuable in the collection due to its silver content and historical significance. 1976 Bicentennial Half Dollars : These were issued for the U. 44 coins 22 Stamps 2-76,2-91,2-79, 2-80, 2-12,2-11,2-13,2-07,2-02,2-99,2-86,2-10,2-97,2-02,2-89,2-92,2-90,2-01,2-82,2-77,2-64,2-04.