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.
Proof coins are struck twice, or more!
Not only are proofs made using specially treated dies, each coin is struck two or more times by the coin die. By striking it more than once the metal is forced into all the crevices of the die, thereby giving a very fine detail to the image on the coin. This fine detail does not appear on some non-proof coins.
I think this covers it................................