The flat-pack packaging continued through 1964, after which the coins were sealed in various styles of hard plasticized cases. (From 1965 to 1967 the production of proof sets was suspended and Special Mint Sets were made in their place. They were made at the San Francisco Assay Office but bore no "S" mintmark.)
Modern Proofs are manufactured in gold, silver and platinum. These coins are sold by the U.S. Mint directly to the public. The mintages of these coins are always a fraction of what is produced for bullion.
Proof Coins: Are the finest quality of coin produced by the United States Mint. The term "proof" refers to the coin's finish. Proof blanks are specially treated, .
U.S. Mint Gold coins are also available in proof sets from APMEX, including a proof coin set of Gold American Eagles in denominations of $5, $10, $25 and $50 .
A newly minted proof coin is also Un-circulated, however it is the way it is made that causes a difference in appearance and qualifies it as a "proof".
The following article will dive deeper into the specifics of both proof and uncirculated coins. Proof coins and Uncirculated coins are both popular among buyers .
The U.S. Mint Proof Sets are a foundation of any true coin collector's collection–in fact, proof sets have always been a popular part of coin collecting.