The double eagle or $20 gold piece was authorized for coinage in March of 1839. It is the largest denomination of regular US issues. It weighed 516 grains; with a fineness of .900. The obverse has a head facing left; there were two reverse designs. The design of 1861 by Anthony C. Paquet was withdrawn soon after being struck.
The Saint Gaudens double eagle minted from 1907 - 1933 is considered to be the most beautiful US coin. It should be noted that coins produced from 1907 through 1911 have 46 stars on the obverse; those produced from 1912 through 1933 have 48 stars.
All double eagles have the same standards. Those being weight 33.436 grams; gold .900, copper .100, with a net weight of .96750.