Ron Guth: The term "American Eagles" encompasses a variety of designs, denominations, and metals issued by the United States beginning in 1986, when the Mint started competing directly with other world coins for a piece of the bullion market. Prior to 1986, bullion buyers focused their attentions on the South African Krugerrand (political issues), the Canadian Maple Leafs (first coins to be made of pure, 24K gold), Mexican 50 Pesos (odd weight), and a variety of other world coins whose value depended solely on their gold content.
The Silver American Eagles debuted in 1986 and have been limited ever since to a $1 denomination. Gold American Eagles first appeared in 1986 and now include $5, $10, $25, and $50 denominations.
In 2006, the Mint produced its first 24K gold coin -- the $50 "American Buffalo". That program now includes $5, $10, $25 and $50 denominations.
The "First Spouse" series began in 2007 as a companion to the Presidential Dollar program. The First Spouse coins are struck in 24K gold, but only in the $10 denomination.
In 2009, the Mint created a copy of the double-thick, small diameter $20 Ultra-High-relief patterns. Although they are part of the Mint's gold bullion programs, their issue price and secondary market price have been significantly higher than the value of the gold they contain
The American Eagle platinum coin program began in 1997 and includes $10, $25, $50, and $100 denomninations. The Proof versions of these coins feature a new and different design each year. In general, the mintages of the platinum coins are extremely low.
Proof and Mint State versions of nearly all of the above coins are available. The denominations are nominal and essentially meaningless, because the intrinsic values of the coins has exceeded their face value from the beginning of the various programs.