The set, contains proof versions of the commemorative quarters honoring 2009 District of Columbia quarter 2009 Commonwealth of Puerto Rico quarter 2009 Guam quarter 2009 American Samoa quarter 2009 U.S. Virgin Islands quarter 2009 Northern Mariana Islands . Proof coins are produced at the United States Mint at San Francisco, using specially prepared, highly polished dies. Specially treated coin blanks are struck multiple times to ensure the finest detail in a frosted cameo image on a brilliant, mirror–like background.