Proof Gold Coins are coins that have been specially struck for collectors and special occasions. They are not meant for circulation. Proof is not a grade but a designation for coins that have been struck, usually as preproduction samples.
The blanks from which the coins are made are usually specially prepared and are polished before being struck by the die. The dies themselves are specially prepared and polished also prior to the strike. This give the coin a special finish as proof coins are expected to be perfect. Strictly speaking any coin which is absolutely perfect is referred to as being in F.D.C. condition, an abbreviation of fleur de coin. The literal translation of fleur de coin is ‘flower of corner’ but is more taken to mean the flower of coins, i.e. the best possible, perfect.
There are different types of proof coins. Some are produced with a matt finish. Some have a reverse proof finish. The background is matt and the raised design is polished.. But most proof coins, and the ones that the majority of collectors look for, is the traditional matt design on a highly polished background.
With proof coins there is a stringent quality control with each coin being inspected for flaws. If one flaw or blemish is found the entire batch is usually checked and rechecked.
Proof coins are usually packed into capsules and a high quality display packaging along with information about the coins. Gold coins are soft and proofs, especially, should not be removed from the packaging which has been designed to protect the coin from nicks, scratches and any other blemish.
Proof gold coins are produced in limited amounts and runs, so are more rare than the uncirculated. This can only improve their value as time marches on. In times of economic need they are an excellent source of funds as they can always be sold.
From 1999 to today, the price of gold bullion has risen from 330 to over 500 dollars an ounce, while the value of a one ounce "Proof" American Gold Eagle went from $525 to over 700 dollars.
If you want to collect only the best of the best in gold coins, you could not do better than collect proof gold coins.