How to grade bank notes, according to Whitman's Official Guide Book of United States Currency, 3rd Edition:
Choice Crisp Uncirculated (Ch. CU)- An almost perfect new note, of only slightly less than gem quality. Centering may be just a little off. It may show slight aging or light counting smudges or wrinkles.
Crisp Uncirculated (CU)- No trace of circulation or folding. May not be perfectly centered, and can have a few defects such as pin holes, counting smudges, wrinkles, close margins or a corner tip fold that does not extend into the design.
About Uncirculated (AU)- Only slightly less than the definition of Uncirculated. Close examination will show minor imperfections. Light folds may be noticeable but not sufficient to break the paper or impair the design. May have corner folds, but no fading or mutilation.
Extremely Fine (Ex. Fine)- Note shows light circulation but still has most of its crispness and is bright and attractive. May have some folds and minor imperfections.
Very Fine (VF)- Shows some evidence of circulation and handling; but is still bright, not badly soiled and without tears. May show several folds and will have lost some of its crispness and color. Notes that have been cleaned or pressed will grade no higher than Very Fine.
Fine- Shows considerable circulation but is still quite clean and has very little crispness left. Edges may be rough or torn, but no portions may be missing. Must not be badly stained or faded.
Very Good (VG)- Will be fairly well soiled and may be significantly worn. Edges can be rough and corners rounded. Notes may be lightly stained or faded with little or no crispness.
Good- Only the rarest notes are collected in "Good" condition. These pieces are well worn, may have tears on margins, and even a stain or ink mark. They have generally lost all crispness and may be soiled, limp and somewhat unattractive.