The U.S. Bicentennial coins that preceded America250 carried the double date 1776–1976.
The United States Mint issued special circulating designs for a quarter, half dollar, and dollar to commemorate the 200th anniversary of American independence. The coins were struck in 1975 and 1976, but all bore the combined dates 1776–1976.
The quarter featured a colonial drummer, the half dollar showed Independence Hall, and the dollar depicted the Liberty Bell superimposed on the Moon. These temporary reverse designs made the anniversary visible in everyday commerce.
The double date can cause confusion because some coins were physically minted in 1975. The dates refer to the historical span being celebrated, not necessarily the year in which a particular coin was struck.