Brilliant Uncirculated coins are high-quality coinage produced by top mints as a middle tier between the most expensive proof coins and the mass produced bullion coins. These coins, often depicted by the letters BU, B.U, or B.UNC, are struck twice by a hand-etched die (stamp) for a clearer image on each side of the coin.
Brilliant Uncirculated coins are struck twice, compared with only once for Bullion coins but six times for Proof coins. The result is that they lack the mirror finish of Proof coins but do boast an excellent contrast and a very sharp image on both sides of the coin.
To speed the process up these coins are machine-fed, meaning refiners like the Royal Mint can make 100 Brilliant Uncirculated coins per hour.
Many of these B.U coins are boxed and come with a certificate of authenticity, but some - especially if second-hand - can be sold in a protective plastic coin capsule.