I'm looking at a used lens with a "D" rating
N = New Comes complete as packed by manufacturer with warranty except where noted.
D = Demo Demonstration condition almost like new, might show very light use.
E+=Excellent + Very clean
E = Excellent Shows normal wear, might have minor scratches, glass clean.
E - = Excellent - Average wear, may have small marks but no brassing
V = Very Good Shows heavier wear, works mechanically fine
G = Good Shows extra heavy use wear, glass might have scratches, usable
F = Fair
I'm likely to purchase it I just hope it really is a "D"..