On 2014-11-25 13:32:44 +0000, Tzortzakakis Dimitris said:

by looking at it, it's no wonder it costs an arm and a leg!!but surely
you can take amazing photos with it, despite all its aberations.is that
the M42 mount, which had my soviet Zenit? On later Zenits they had the
pentax K-2 mount. I had an 28 mm wide, a normal 50 mm and a 120 mm tele
IIRC.They were quite good, altough nothing to do with my Nikkor
50mm1.4, sigma 24 mm2.5 and tamron 70-210 zoom!!although the tamron was
quite crappy.

It's not for the M42 mount, it's for the Leica screw mount aka M39.