I usually will under grade slightly. Here is my system: 1. NEW/MINT: means exactly that, no flaws.
AS NEW/NEAR MINT: means there may be very some tiny flaw such as some very minor rubbing. FINE: means there may be slightly more imperfections, such as some wear or a tiny crease, etc. VERY GOOD: means there are flaws, such as pinholes, small closed tears, spots, rubbing, creases, chips, staining, discoloration, etc.All of which would be minor. GOOD: means that there are significant problems. Holes, tears, pieces missing, smoke damage, mold, insects, dents, cracks, parts missing, incomplete items, water staining or damage, sunning, loose pages, bindings, covers.