large numbers of half dollars are typically held by banks or available to order, they are often sought after by coin roll hunters for the purpose of searching for silver coins, proofs, and coins not intended for circulation. The Presidential Dollar series features portraits of all deceased U.S. Presidents with four coin designs issued each year in the order of the president's inauguration date. These coins began circulating on February 15, 2007. Starting 2012, these coins have been minted only for collectible sets because of a large stockpile. The Susan B. Anthony dollar coin was minted from 1979 to 1981 and 1999. The 1999 minting was in response to Treasury supplies of the dollar becoming depleted and the inability to accelerate the minting of the Sacagawea dollars by a year. 1981 Anthony dollars can sometimes be found in circulation from proof sets that were broken open, but these dollars were not minted with the intent that they circulate. Although dollar coins have not been struck for circulation since 2011, the American Innovation dollar is considered a circulation coin by the US Mint. Since 2019, each American Innovation dollar coin features a different privy mark, changed annually, located just below "IN GOD WE TRUST". Bullion coins Non-circulating bullion coins have been produced each year since 1986. They can be found in gold, silver, platinum (since 1997), and palladium (since 2017). The face value of these coins is legal as tender, but does not actually reflect the value of the precious metal contained therein. On May 11, 2011, Utah became the first state to accept these coins as the value of the precious metal in common transactions. The Utah State Treasurer assigns a numerical precious metal value to these coins each week based on the spot metal prices. The bullion coin types include "S" (San Francisco, 1986–1992), "P" (Philadelphia, 1993 – 2000), and "W" (West Point, New York, 2001–present). Commemorative coins Modern commemoratives have been minted since 1982. A list is available here. Mint marks List of current and past United States Mint branches and mint marks found on their coins: Obsolete and canceled coins Half cent: ¢, 1793–1857 Silver center cent: 1¢, 1792 (not circulated) Large cent: 1¢, 1793–1857 Ring cent: 1¢, 1850–1851, 1853, 1884–1885 (not circulated) Two-cent billon: 2¢, 1836 (not circulated) Two-cent bronze: 2¢, 1863–1873 Three-cent bronze: 3¢, 1863 (not circulated) Three-cent nickel: 3¢, 1865–1889 Trime (Three-cent silver): 3¢,