I know for sure that EL's oiginal 100 was the first to be produced. There are some slight differences most certainly with the dial (markers/lume), and possibly with things like the case back, overall finising, engraving etc. I can't really say for sure whether these latter differences are intrinsic or even palpable by physical examination only; I've not had an EL100 and a 3rd generation example in hand to review side by side.
I can say for certain that the dials are different, and this may or may not be the selling point. The original EL100 is easier/better for relume work due to the construction of the luminous markers. The V3 is more problematic as the markers are applied differently, and stand to risk more damage to the dial upon removal.
Aside from that, I am not certain if there are any major differences with case or bracelet otherwise.