Eagle (United States coin)

Gold eagles were issued for circulation by the United States Mint from 1795–1933, half eagles from 1795–1929, quarter eagles from 1796–1929, and double eagles from 1850–1933, with occasional production gaps for each type. Except for the double eagle, the diameters of all these denominations were decreased over time. The following table presents the diameters of each of the denominations, in millimeters (mm), according to the first year that diameter was used:

Originally the purity of all circulating gold coins in the United States was eleven twelfths pure gold (the same 22 karats level as English crown gold) and one twelfth alloy. Under U.S. law, the alloy was composed only of silver and copper, with silver limited to no more than half of the alloy by weight. Thus, U.S. gold coins had 22/24 (22 kt or 91.667%) pure gold, at most 1/24 (0–4.167%) silver, with the remaining one–two 24ths (4.167–8.333%) copper.[1]

The weight of circulating, standard gold, eagles was set at 270 grains (17.5 g), half eagles at 135 grains (8.75 g), quarter eagles at 67.5 grains (4.37 g). This resulted in the eagle containing 0.5156 troy ounces (16.04 g) of pure gold.

In 1834, the mint's 15:1 legal valuation of gold to silver (i.e. 15 weight units of silver and 1 weight unit of gold have the same legal monetary value) was changed to 16:1, and the metal weight-content standards for both gold and silver coins were changed, because at the old value ratio and weight content, it was profitable to export and melt U.S gold coins. As a result, the specification for standard gold was lowered from 22 karat (.9167 fine) to .8992 fine (21.58 kt).

In 1837 a small change in the fineness of the gold (increased to exactly .900 fine) was made, and the alloy (now 10% of the coin's weight) was again legally defined as silver and copper, with silver capped at no more than half.[2] (i.e. 5% of total coin weight) The new 1837 standard for the eagle was 258 grains (16.7 g) of .900 fine gold, with other coins proportionately sized.

Between 1838 and 1840, the silver content was reduced to zero—the eagle in 1838, half eagle in 1839, and quarter eagle in 1840,[3]—resulting in U.S. gold coins being 90% gold and 10% copper. Using only copper as the alloy in gold coins matched longstanding English practice (see crown gold).[4] The 1837 standard resulted in a gold content of only 0.9675 troy ounces of gold per double eagle and 0.48375 troy ounces for the eagle. It would be used for all circulating gold coins until U.S. gold coin circulation was halted in 1933.

The three $10 commemorative coins: (1) 1984 Summer Olympics, (2) 2000 Library of Congress, and (3) 2003 First Flight Centennial

As part of its Modern United States commemorative coins program the United States mint has issued several commemorative eagle coins. In 1984, an eagle was issued to commemorate the Summer Olympics, and another eagle was issued in 2003 to commemorate the Wright brothers first flight at Kitty Hawk. The pre-1933 .900 fine gold standard was restored, this would also be used in half-eagle gold commemoratives as well. The coins would be identical in fineness and size to their pre-1933 counterparts of the same face value. In 2000 a unique eagle, the Library of Congress bimetallic eagle, was issued commemorating the Library of Congress; it consisted of equal weights of an approximately 1/4 oz .9995 fine platinum core and a .900 fine gold outer ring.