What exactly is a "proof" coin?

Answer 1

Definition: A proof coin is a coin struck using a special, high-quality minting process, and made especially for collectors. Modern proof coins often have mirror-like fields and frosted devices, although proof coins struck prior to the mid twentieth century are often distinguished only by their high quality surfaces. In all cases, the term proof always refers to a type of coin, or the way it was struck, and not to a coin's grade.

See Also: Reverse Proof Coins
Examples: You should never see proof coins in circulation, because they are made for collectors, and sold by the mint for more than face value.

Answer 2

A proof coin is struck for collectors. The planchet used is hand inspected and it is polished to a high gloss. The die is also special and may have a little more relief that standard circulation dies. the die is also highly polished. The planchet is also struck more than once to make sure all the devices are sharp. As someone said here it is a type of coin and not a grade of a coin. You can have what is called a mishandled proof, one that got spent from a collection. In that case say it only grade very fine it would then be called a Proof for it is one and grade 30, so it would be listed on the holder as PR-30. Proofs also have a mirror finish in the fields and theses days have a frosted image.

Answer 3

Its never been touched by humans. never been ruibbed against other coins, an is sealed in a pack.