In Western Tradition, coin value is derived from the values of the metals from which they are minted.  Interestingly, the American dollar is not, in fact, the only American currency.  The dollar is one of two currencies set forth by Congress in 1792; the other is the American eagle.  The dollar’s value was based on the silver standard, but the eagle on the gold. 

Today, gold collector coins come in many forms.  Circulated coins, such as the Liberty Head and Indian Head gold dollar, were regularly minted from 1849 – 1889.  Thereafter, occasionally commemorative coins were minted for the Panama Canal and President Grant.   After the abandonment of the gold standard in the early 1930’s, gold coins have come out of circulation almost entirely. 

Gold Coins now come in two forms mostly, commemorative collector coins and gold bullion coins.  Bullion coins, like the European ducat or Dutch guilder, are coins that are still valued on the gold standard, or current international market price of their precious metal weight, either silver, gold or platinum.  American gold bullion are minted at West Point in 1/20 oz, 1/10 oz, ¼ oz and ½ oz gold, as well as a full ounce of gold per coin.

Today, auction houses, eBay and numismatic (the study of coins) conventions flood with anxious collectors, hoarders and investors who are looking for that rare gold coin
Buying and selling at market values bullion coins has only been a tradition since the Krugerrand was first minted in 1967 to stabilize the S. African Market, but collecting antique, old and commemorative coins has been the Hobby of Kings since the 15th Century.