Produced by the United States Mint at San Francisco, each proof quarter bears the “S” mint mark of that facility. These quarters are produced from carefully selected planchets, or coin blanks, that have been burnished to a high luster. The polished blanks, which are carefully handled to minimize scratches and abrasions, are struck on specially adapted coining presses. Each coin is struck at least twice to bring forth the most minute detail with remarkable clarity.
U.S. Proof Coin Sets: 2009 U.S. Territory Quarters
2009 District of Columbia and the U.S. Territories Quarters Proof Set