Every single one of those is different than the other. Not just missing (or not) the "600"
I don't know much abut these in particular but I will say just based on those pictures alone the ones that are missing "600" have a date window.
The ones that do say "600" do not.
Not sure if that is a hard/fast rule though. Also, those examples w/ date window and no "600" also have alpha hands. The other, baton and not even the same baton.
Also watch out for re-dials. But none of these are super obvious to me in this case, at least not with these pictures.
I'm also still learning so I'm taking a stab at this for fun (and correction).
First picture, wrong case. 2nd and 3rd, may be all correct, but again "600" and date differences and hand difference (probably due to year produced). 4th picture looks like an entirely wrong hand set.