I have somehow ended up with 3 135's: a 135/2 AiS, a 135/2.8 AiS, and a 135/3.5 Ai. They all are different lenses, of course, but they have a remarkably similar rendering. or 'look'. The older Q designs should render more noticeably different from the later Ai/AiS units, but I haven't shot with the older designs on digital...yet.