$20 Double Eagle | United States Gold

Regular issue double eagles come in two major types and six minor varieties as follows:

Liberty Head (Coronet) 1849–1907
Liberty Head, no motto, value “TWENTY D.” 1849–1866 (Type I)
Liberty Head, with motto, value “TWENTY D.” 1866–1876 (Type II)
Liberty Head, with motto, value “TWENTY DOLLARS” 1877–1907 (Type III)

Saint-Gaudens 1907–1933
Saint-Gaudens, high relief, Roman numerals, no motto 1907
Saint-Gaudens, low relief, Arabic numerals, no motto 1907–1908
Saint-Gaudens, low relief, Arabic numerals, with motto 1908–1933

A double eagle is a gold coin of the United States with a denomination of $20. Its gold content of 0.9675 troy oz (30.0926 grams) was worth $20 at the 1849 official price of $20.67/oz.)
The eagle, half eagle, and quarter eagle were defined by name in the Act of Congress originally authorizing them. Likewise, the double eagle was created by the Coinage Act of 1849. Since the $20 gold piece had twice the value of the eagle, these coins were designated “double eagles”. Before, the most valuable American coin was the $10 gold eagle, first produced in 1795, two years after the United States Mint opened.