Pepe
I think you may need to ask another member, first, I think there are 2 versions, and second, I don't own it. In fact, when I started out, my first and only 135 was the K135/2.5 which is arguably the best 135 in terms of not just sharpness but also speed, etc even wide open. So let's say I began with the "gold standard"
When I put together my M42 kit, I avoided where ever possible getting SMC Taks, because I wanted lenses that would give a different look than my K mount lenses. What I did not mention, but which I also own, is a tele lentar 135 F2.8 preset with 14 aperture blades. It is every bit as good as the SMC Tak 135/3.5 which is also a very nice lens, but the difference in optical design between the preset and the SMC tak is sufficient that the Tele Lentar Preset seems to give a more 3D image. By this I mean that the out of focus area at any aperture has more real separation than with the Tak. I ran a 3 lens comparison a while back with these two lenses plus a 3rd 135, and posted the results.
I picked up the SMC tak and the M 135 F3.5 lenses much later, and really only because I got them at really good prices. Certainly I don't
need them