Definition: A BU coin is a coin that has never been circulated, and retains all of its original mint luster. BU stands for Brilliant Uncirculated. This term is used less frequently now that the Sheldon scale of numerical grading has come into vogue. A BU coin is usually described as MS (Mint State) today, and generally falls into the lowest MS grades (MS-60 through MS-62.) Higher MS grades are designated as "Choice BU" (MS-63 and MS-64) and "Gem BU" (MS-65 plus).
Also Known As: Mint State (MS)
Alternate Spellings: B.U.
Examples:The old 2x2 coin holder said that my 1898 Morgan Dollar was BU, and sure enough, it came back from PCGS graded MS-60.