The U.S. had largely stopped striking proof coins in 1916, although a few later specimens exist. Beginning in 1936, the U.S. Mint began producing proof sets. Sets struck from 1936–42 (1942 offered a five-coin and a six-coin version, the latter included the silver wartime nickel) and, when resumed, from 1950–72 include the cent, nickel, dime, quarter, and half dollar. From 1973 through 1981 the dollar was also included, and also from 2000 on.

From 1950 to 1955, proof sets were packaged in a box and each of the five coins was sealed in a cellophane bag. 1955 saw both the original "box" packaging and introduced the flat-pack, where the coins were sealed in cellophane and presented in an envelope. 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. 

What's a proof coin?

   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".  To understand this, let's look at how coins are made.  Coins are produced when two dies strike a blank piece of metal with tremendous force. One die is engraved with the front (obverse) design for the coin.  The other die has the back (reverse) coin design on it.  

A proof coin is made with a specially polished and treated die!

   By treating the die in a special way, the coins it produces have a different appearance.  Modern technology allows the high points on the coin design to be acid treated (on the die).  The background (field) design of the coin die is polished, resulting in a mirror-like look on the coin it strikes. This gives the finished coin a frosted look (frosting) on the raise parts of the design, with a mirror like finish on the background. This contrasting finish is often called "cameo".  (See picture above.) On some older coins a cameo appearance is quite rare. The attribute "CAM", when added to a coin's description, means cameo appearance. "DCAM" means deep cameo, and indicates the cameo appearance is strong and easy to observe. 

Rarity and the Cost of Proofs

   Because of the extra effort, time, labor and production costs in making a proof coin, the respective government mints often sell them at higher prices.  In many instances the production of proof coins is limited.  The end result is that usually, but not always, a proof coin of the same date will be more expensive than a non-proof uncirculated. 

• 1977 Proof Set
• Polished and Double Struck
• Uncirculated
• Original Case