Grading an item from fair to mint condition is subjective and it might vary from person to person, but here are our guidelines we follow here at Fetch the Paper.
Mint (M): The page is perfect in every way. No smell, damage, discoloration or damage to the edges. (<1%)
Near Mint (NM): The page is nearly perfect. (15%)
Very Good Plus (VG+): The page is very good (35%)
Very Good (VG): (45%)
Good, Good Plus (G, G+): (<5%)
Poor, Fair (P, F): The pages in this condition are not 100% complete or have damage to the point that most would consider them trash, however this may be a piece of advertising that's rare or a piece of history that needs to remain in a collection for future generations. (<1%)