1976 was the 200th anniversary of American independence. To help celebrate the event, the backs of three circulating coins were given a special design. This was the first time in American history that any circulating coin came out with new designs for a special occasion that were made for only a short period of time. In this case, these designs were made in 1975 and 1976, though none shows a 1975 date; all say “1776–1976.”
To find out more about these coins, check out the United States Mint H.I.P. Pocket Change™ Bicentennial Coins page.