On the NGC Forums, there was a discussion about collecting gold dollars where someone asked about their composition. Being curious, I looked up the composition information. What I found was that there were different compositions that was tied to the evolution of US coinage.
After posting the basic information, I thought it would be interesting to look up which series of gold coins were made from each of the different compositions. The rest of this posting is what I found after consulting a few references.
The Coinage Act of 1792, the First Coinage Act, set the standard for gold coinage to be .9167 fine with the balance of silver and copper. Gold coins struck 1792-1834 were made of this composition. These coins include:
- Turban Head $2½ Quarter Eagles (1796-1807)
- Capped Bust $2½ Quarter Eagles (1808-1834)
- Capped Bust to the Right $5 Half Eagles (1795-1807)
- Capped Bust to the Left $5 Half Eagles (1807-1812)
- Capped Head to the Left $5 Half Eagles (1813-1834)
- Capped Head to the Right $10 Eagles (1795-1804)
The Coinage Act of 1834, the Second Coinage Act, set the price of gold at $20.67 and changed the composition to .8992 fine with the balance of silver and copper. Gold coins struck from 1834-1839 were made of this composition. These coins include:
- Classic Head $2½ Quarter Eagles (1834-1939)
- Classic Head $5 Half Eagles (1834-1838)
The Coinage Act of 1837, also called the Bland-Allison Act, put the US on a bimetal monetary standard mostly to help the silver industry following the Panic of 1873. Originally, President Rutherford B. Hayes vetoed the bill only to have congress override the veto. Gold coins struck from 1839-1933 were made of .9000 gold and the balance was silver and copper. These coins include:
- Liberty Head One Dollar (1859-1854)
- Indian Princess Dollar (1854-1889)
- Liberty Head $2½ Quarter Eagles (1840-1907)
- Indian Head $2½ Quarter Eagles (1908-1929)
- Indian Princess 3 Dollars (1854-1899)
- Liberty Head $5 Half Eagles (1839-1908)
- Indian Head $5 Half Eagles (1908-1929)
- Liberty Head, No Motto Above Eagle $10 Eagles (1838-1866)
- Liberty Head, Motto Above Eagle $10 Eagles (1866-1907)
- Indian Head $10 Eagles (1907-1933)
- Liberty Head $20 Double Eagles (1849-1907)
- Saint-Gaudens $20 Double Eagles (1907-1933)
All gold commemoratives, both prior to 1933 and since 1982, are struck using .9000 gold. Commemorative struck before 1933 was filled with 1-part silver and 2-parts copper. Commemorative coins struck since 1982 use a 2-part copper to 1-part nickel filler.
The $4 Stella patterns were an attempt to create a standard coinage composition for international trade. The composition called goloid was made of 6 grams of gold, 0.3 grams of silver, 0.7 grams of copper. A Flowing Hair and Coiled Hair Liberty Head patterns were struck in 1879 and 1880.
American Gold Eagle bullion and proof coins are .9167 gold (22 carat). The one ounce gold Eagle contains one troy ounce of gold plus .0909 troy ounces of filler consisting of 2-parts nickel to 1-part copper.
The American Buffalo gold coin contains one troy ounce of .9999 fine gold (24 carat) with copper as the filler.
I hope someone finds this useful.