For our current pricing we use https://www.priceguide.cards/en
Pristine (10) - Centering 50/50 all around, corners perfect to the naked eye and Mint under magnification, no print spots, perfect gloss, devoid of any surface flaws.
Gem Mint (9.5) - Centering 50/50 one way, 55/45 the other. Corners Mint to the naked eye but subtle wear is allowed under magnification, smooth edges, a few extremely minor print spots detectable under intense scrutiny.
Mint (9) - Four sharp corners (a tiny speck of wear is allowed), 55/45 or better centering, smooth edges, original color borders and gloss, a handful of specks or one minor spot.
Near Mint-Mint (NmMt 8) - Must have 60/40 or better centering, relatively smooth edges, original color borders and gloss. One of the following very minor flaws is allowed: corners sharp to the naked eye but slight imperfections under intense scrutiny, a handful of minor print spots, subtle color or focus imperfections.
Near Mint (NrMt 7) - Centering of 65/35 or better. In addition one of the following minor flaws is allowed: a slight touch of wear on two or three corners, slightly rough edges, a few noticeable print spots or speckling, color or focus imperfections.
Excellent-Mint (ExMt 6) - Centering no worse than 70/30. No more than two of the following flaws are allowed: two or three fuzzy corners, slightly rough edges, very minor border discoloration, noticeable print spots, color or focus imperfections.
Excellent (Ex 5) - Centering no worse than 75/25 with four fuzzy corners (a touch of notching or a minor ding is allowed). May also have rough edges, minor border discoloration and noticeable print spots, color or focus imperfections.
Very Good (VG 3) - Handled, but not abused. Centering 80/20 or better. Slightly rounded corners with slight layering, slight notching or noticeable chipping on edges, moderate border discoloration, some gloss lost from the surface, very minor scuffing. May have hairline creases.
Good (2), Fair (1.5), Poor (1) - Well-worn or abused. Badly rounded and layered corners, scuffing, no original gloss, major border discoloration, and serious creases.