The following is excerpted from Clifford Mishler’s Coins: Questions & Answers
Q: Is it true that one of the current regular-issue coins of the United States has also served as a commemorative coin?
A: The Washington quarter was first issued in 1932 to commemorate the 200th anniversary of George Washington’s birth. When regular coinage of the quarter was reintroduced in 1934—the last Standing Liberty quarters were produced in 1930, with no quarters being minted in 1931 or 1933—the Washington quarter commemorative had been so favorably received as the nation’s second presidential coin that it supplanted its predecessor as a regular-issue coin. It again became a commemorative during 1975 and 1976 when the “Drummer Boy” Bicentennial commemorative design was adapted to the reverse. The designs reverted to John Flanagan’s originals commencing in 1977, continuing through 1998, at which time the obverse design was modified to incorporate the country name and denomination which previously appeared on the reverse.