Gold Eagles are the official bullion coin of the United States and legally can only be produced with gold that was mined in the U.S. The Gold Eagle made its debut in 1986 and has a gold composition of 91.67 percent and is 22 karats. The rest of the coin is made up of 3 percent silver and 5.33 percent copper, to provide the coin with strength and prevent it from getting scratches and marring. Gold Eagles are backed by the United States government for their weight and purity, which are measured in troy ounces. Troy ounces are the measurement units which are used to price and weigh precious metals.