PK-fit Elmar's head (Was: PK mount lenses)

[Andre Langevin]

I have an Elmar 135 f4 (M).  Can I unscrew the head?

I can only unscrew a little aluminum ring under the aperture ring.
It uncovers some screws.  Should I go on?
If it unscrews, I could maybe adapt the head to a Pentax zoom tube.

Andre