Vinicio:
Sorry for getting your name wrong the last time. Yes, the construction is identical, and the elements are held at exactly the same distance when the lens is new, on paper, but would brass hold up better than aluminum in the long run, or vice versa, after a lot of hard knocks in real life, actually taking pictures? If there is a difference in strength, after a couple of years of hard use, the elements might be knocked out of alignment easier with one than the other. Maybe so, or maybe not. But this is question I was asking, based on someone's real life experience of actually taking pictures. Does anyone have any experiences like this? US$ 2,500 is still a lot of money to dish out, and I'd like to think that the lens mount was durable.