Proof coinage
Proof coins are created especially for
coin collectors. Modern US proof coins have polished fields and frosty devices. Several methods of proof production have been used in the past including sand blasting (the dies, not the coins), and matte proofs. Proof coins of the early 1800s even appear to be scratched, but it was part of the production process.
Most proof coins are double struck. This does not normally result in doubling that is readily observable, but does result in the devices being struck fully.
See also Commemorative Coins