The American Gold Buffalo is the United States Government’s bullion coin, produced from pure 24k gold. This was done to compete with other countries that had produced their bullion coins from pure gold. James Earle Frasier produced the original design and borrowed from the United States Buffalo and Indian Head Nickel. The American Gold Buffalo is commonly found in the 1 ounce or $50 denomination. However, there are 1/4 ounce ($10) and 1/2 ounce ($25) bullion coins that command a premium because of their lower mintage.
Coin images courtesy of PCGS Coinfacts