Antonio asked: "Can anyone tell me how important the matt black metalic letterbox is on k mount fixed lenght lenses, as one seems to have come unstuck on my 135/2.5 and was wondering if it was necessary at all to stick it back on (not an easy job as I would have to somehow get it perfectly horizontal again). I notice that the earlier M42 mount versions of this lens didnt have the letterbox .."
I believe that they're baffles and their purpose is to reduce reflections off the inside of the lens barrel. I don't know this for sure but it's the only useful purpose I can imagine. Some longer lenses have more than one of them. I had one come loose on a lens once and I very carefully used a couple drops of crazy glue to put it back. I don't remember which lens I fixed. Tom Reese
