In order to met the need for a trade coin to compete with Mexican 8 real or peso in the Orient, production of Trade Dollars was begun in 1873. The weight of the Trade Dollar was set at 420 grains which was 1.8% heavier than a standard Silver Dollar. The Trade Dollar was intended for export only, however they were still legal tender in the U. S. until 1876 when congress changed that status. Many of the Trade Dollars that circulated in the Orient were counterstamped with an Oriental chop mark that merchants used to reaffirm the silver content. Some have an abundance of these chop marks. Production of quantities of Trade Dollars continued through 1878 after which only small quantities were produced for proof sets through 1883. 1884 and 1885 proofs are very rare. In 1887 congress repealed the authorization for trade dollar production and authorized their redemption.