The United States trade dollar is a silver (fineness of .900 or 90%) dollar coin that was issued by the United States Mint and minted in Philadelphia, Pennsylvania, Carson City, and San Francisco from 1873 to 1885. Business strike trade dollars were last produced in 1878 and proof coin production continued until 1885. The coin weighs 420 grains (27.2 g), about 8 grains (0.52 g) more than the domestic silver dollar (Seated Liberty Dollars and Morgan Dollars) of the time. It is 4 grains heavier than the Mexican peso; however, the peso is .903 silver.