The Gold Standard Act of 1900 abandoned the bimetallic standard and defined the dollar as 23.22 grains (1.505 g) of gold, equivalent to setting the price of 1 troy ounce of gold at $20.67. Silver coins continued to be issued for circulation until 1964, when all silver was removed from dimes and quarters, and the half dollar was reduced to 40% silver. Silver half dollars were last issued for circulation in 1970. Gold coins were confiscated by Executive Order 6102 issued in 1933 by Franklin Roosevelt. The gold standard was changed to 13.71 grains (0.888 g), equivalent to setting the price of 1 troy ounce of gold at $35. This standard persisted until 1968.