The highest standard of bullion coin finish. Uncirculated collector's coins come in three types: Proof, Brilliant Uncirculated and Bullion. Historically, proof coins were struck to check the die or as archival samples. Today, mints issue proof coins for numismatists who want coins that are finished to exceptional standards. BU Coins are made by striking a blank piece of metal with two dies – one engraved with the reverse design and one with the obverse design. Proof coins are created by striking the coin more than once with a die that has been specially treated and polished to give the design a frosted look in contrast to a highly polished, mirror-like background. By striking the coin with the die twice or more, metal is forced into all the crevices to create a finely detailed appearance. Discover our remarkable range of gold and silver proof coins now at coininvest.com.