I believe it was a cine lens originally, fortunately not anamorphic. I guess some machinest has made it into an M42 lens. Clearly, it is not up to today's standards - and yet, I find I like the way it fails, if you know what I mean. I don't just mean bokeh or DOF effects, although surely a 150mm lens at f2.3 has a ton of that. I mean edge-to-edge sharpness is not present in a very obvious way - like the old Petzval lenses once used for LF portraiture. A happy coincidence.
Best Regards,
Bill Mattocks