Oops, I've only just read Ron's brief tutorial on another Pentax lens (Takumar 35/3.5) and the assembly looks quite the same on the front as he describes. You need special tools or two brothers to unscrew the parts... I've managed to remove the front text thingy though (with an axe) ;-) Forgot to mention that the diaphragm ring goes heavy and the aparture does not close completely on smaller settings say smaller than F11. So dismantling is my only option?