One of the oldest forms of money is gold coins, and they have enjoyed the status of being the primary form of money for a very long period of time.

At around 560 BC, King Croesus of Lydia is said to have coined the first gold coins in the history of mankind, and in 700 BC, King Pheidon of Argos minted the first silver coins. During the sixth or fifth century BC, the Chinese started minting the Ying Yuan, their gold coin. The twentieth century, however, saw the decline of gold coins as a form of money, and their disuse finally became apparent and ascertained in the 1930s when the world felt the terrible economic crisis of the Great Depression.

While countries the world over have stopped making and using gold coins, gold-colored coins have successfully made a comeback and have enjoyed patronage in several currencies. Furthermore, there are some countries that continue to make legal tender gold coins not for circulation, but for collecting and investment purposes. When Double Eagle coins were struck by the US Mint in 1933, they were surrendered and melted down, leaving only a few of them to survive. Then, in 2002, Sotheby's sold a very rare $20 1933 Double Eagle gold coin for $7,590,020, which is record-breaking and makes the said coin the most valuable coin ever sold. Collectors are known to covet the Solidus, Aereus, and Spur Rval.

There are several factors that determine the value of a gold coin, including its age, condition, rarity, and the number originally minted. For most of history, however, the correct amount of the precious metal it should contain was the basis for the value of a gold coin. The right weight and purity, which is also called as fineness, were given more importance than on the factuality of where a gold coin was said to be made and under which party it was ordered to be made. To avoid time-consuming tests in transactions that take place every day, the genuine appearance of a gold coin was referred to.

A gold coin is denser than a silver coin and all other coins made by other metals. This characteristic makes gold coins incredibly hard to fake, since the tests of volume and weight prove enough to determine a gold coin's genuineness. Platinum is denser than gold and costs more, so it would be futile to use them to fake gold coins. Other metals are either too light or cannot be made into the right coin size. In theory, fake coins could only be made by uranium, thus making the dilemma a most unpractical one. Indeed, it is mission impossible to fake even just one gold coin.

However, there are counterfeit gold coins in circulation and they appear to be well-made. The Saint-Gaudens Double Eagle omega counterfeit, for example, is notorious for its complexity and has managed to fool and mislead several numismatics experts. There are also poor counterfeits. Some double eagles contain gold and copper alloys have not been thoroughly mixed and have a mottled appearance; others do not use the correct amount of gold and weigh less; and still others are larger or smaller in size.