Originally posted by Litov I took a picture of the front element! I will show it now.I have had the lens for two years. I still could not find information about him, except for a German forum.
That's curious. I doesn't look quite like any of the ones that I linked to from the PF lens database. The shape looks most like the Tokina, but it has a 72mm filter thread, not the 67mm one on your lens.
I'd suggest you post these photos (of the lens and some samples taken with it) in the long lenses thread:
300mm plus Lens Club: discuss your long lenses - PentaxForums.com
People there know a lot about old telephoto lenses.