The coinage of legal-tender gold was authorized by the first coinage act passed by Congress, April 2,1792.

The gold unit of value is the dollar, which contains 25.8 grains of standard gold .900 fine. The amount of fine gold in the dollar is 23.22 grains, and the remainder of the weight is an alloy of copper. While the gold dollar is the unit and standard of value, the actual coinage of the $1 piece was discontinued under authority of the act of September 26, 1890. Gold is now coined in denominations of $2.50, $5, $10, and $20, called respectively, quarter eagles, half eagles, eagles, and double eagles.

The total coinage of gold by the mints of the United States from 1792 to June 30, 1908, was $2,993,448,703, of which it was estimated that $1,535,401,287 was in existence July 1, 1908, as coin in the United States, while the remainder, $1,458,047,416, represented the excess of exports over imports and the amount consumed in the arts. The gold bullion in the United States July 1, 1908, was about $80,800,000.

The basis for the estimate of the amount of gold coin in the United States was established in 1873, when the amount in the vaults of the national banks and in the Treasury was ascertained from reports to be $71,188,-548. To this was added $20,000,000 as an estimate of the amount of gold in use on the Pacific coast, $10,000,-000 as the amount held by all other banks and by the people and $3,818,086 in national banks. The amount thus ascertained was $105,006,634, to which have been added each year the new coinage reported by the Director of the Mint and the imports as shown by the custom house reports, and from which have been deducted the exports and the amounts consumed in the arts. It will be seen that more than one-half of the gold coins struck at the mints of the United States have disappeared from circulation.

[The Director of the Mint in 1908 revised the estimates of the amount of gold in the United States, and as a result of the revision the amount was reduced by $135,000,000.]