"Proof" is not a grade but is a method of manufacture. Proof coins are usually struck multiple times from highly polished dies to obtain the high detail and extreme lustre. As a result Proof coins may be found in circulated grades to the highest grades of Uncirculated. "BU" is shorthand for Brilliant Uncirculated. Plain "UNC", or uncirculated coins, may display little to no lustre while "BU" coins have considerable lustre. "AU" is shorthand for Almost Uncirculated or About Uncirculated. An AU coin may have higher eye-appeal than an Unc. coin due to it's lustre, but would exhibit traces of wear on the highest points of the coin. Coins are graded on a numerical scale from 1 to 70, with 70 being the highest grade. Uncirculated grades are assigned MS (Mint State) numbers from 60-70. MS60 is translated as Unc. AU grades are assigned MS numbers from 55-59. Chips should not be graded using a MS system.