You should sign up to this type of forum;
http://www.movieposterforum.com/ and
http://www.movieposterchat.com/ and also this site;
http://www.learnaboutmovieposters.com/ which has a department given over to JB at some part of the site - but I'm damned if I can now locate it via the search. Better of just searching for Dr No and going from there.
But this site has loads of images from the world over, which, combined with the forums, should tell you everything you need to know.
So;
NSS numbers are good to search for on 1 Sheets, bottom right.
There were a reprinted series of Bond posters for a festival in the 80s, they were restruck from the originals so they WILL have the correct date of initial release, but no NSS info. They are sort of collectible but if you're after the real thing, stick with initial release.
Reprinted Gf posters can have a black background as opposed to the correct green.
There are two Thunderball 1 sheets, one that has the jetpack going over the top poster framing line, and one that gets cut off at said line.
More modern ones. The US TND teaser had two versions, one with a foil 007 in the middle, and one without. The one with was withdrawn due to catching fire in the lightbox.
So, there's tonnes to learn but over time, it'll all slot into place.
Good luck.