Grading is an art, not a science. It is subjective, so it may vary depending on the person grading. The following is my grading criteria. All items in unbroken condition will be given a condition as follow:
C10: Given to sealed items only. "Virgin"
C9.5-C10: Highest grade given to an unsealed item.
C9.5+: Has very little to no blemishes.
C9+: May have a very light trace of handling and very light sticker wear.
C9: May have a light trace of handling and light sticker wear.
C8.5: May have traces of handling, sticker wear, and chrome/paint wear.
C7: May have considerable sticker wear and flaws. May have some discoloration.
Notes on abbreviation:
MISB: Mint in sealed box
MIBS: Mint in box, sealed (bubble)
MIB: Mint in box
MOSC: Mint on sealed card
MOC: Mint on card (or with card)