I'm far from being an expert on this. But my layman's perspective tells me that "sonnar" is a Zeiss term, not Leica. Also the zone-focusing numbers and the graphics(?) on the lens looks ... 'fake'. I don't know why it looks fake, but to me it does. Also, the metal chrome doesn't look genuine too. Again, I don't know why it doesn't look genuine to my layman's eyes but it does.
There are a lot of stories behind the 5.8cm F1.5 Sonnar- including they were manufactured for use in gunsights and left over optics were converted to Leica mount after the war.
My take- lots of spare parts from Zeiss were taken back to the USSR as war reparations, and lots stayed with Zeiss. The factories were in shambles in both countries. In Russia, many lenses were assembled as production of the Jupiter series ramped up. In Germany, many one-offs and hacked together lenses were made and sold to occupying forces. I've seen several Sonnars "hacked" together from whatever was available. Not fakes, as to "fake something" there has to be a regular production of the lens. "Hacked Together" while the factory was in shambles, using whatever parts and tools available- that's my explanation. My "Hacked Together" Sonnar was sent to me for repair. The middle triplet was unfinished- meaning half the front surface was not properly polished. I replaced it, performed beautifully. The Mount: ROUGH, UNEVEN- lots of filing. Was it a fake? Not in my book, more a one-off assembled out of unfinished parts by Zeiss factory worker trying to survive. I traded one of my converted pre-war Sonnars for the lens, as it interested me and I needed lots of time to make it work.
Details auf den Abbildungen. Focusing is smooth and easy to focus. The evaluation of our Service is very important to improve what we do. See pictures for detail. No scratches / no separation / no haze / no fungus / inside or on the optics.
The sellers location of the Czech Republic potentially adds to the theory of these lenses coming out of the shambles of post WWII USSR.
This is a "ZK" Sonnar, German optics, German fixtures and focus mount- all finished in Russia. If you take the focus mount apart, you find German serial numbers stamped into the parts. I have one from the same year.
Sorry to come back late on my own question. I used "Fake" in the sense that the "branding" itself is not consistent with a known "legitimate" product in that:
i) Use of Leica and Sonnar together, when Sonnar is a Zeiss product (though it should be said that Leica have worked with other lens manufacturers)
ii) Use of the name Leica, when older "Leica" lenses were marked Leitz (I can't remember when lenses started being branded Leica but it is quite late)
iii) The unusual 58mm focal length which isn't the norm for an f1.5 Sonnar
As Brian has said before, some of his wonderful creations will likely cause confusion with collectors in the future.
In searching around I have seen this same lens without the "Leica" branding but with a close serial number.
I suppose at the end of the day, all lenses are "real" as long as they pass light, but the story of the branding on this one may be lost in time. Though the existance of multiple stories around the 58mm length sounds intriguing.
Many of these lenses seemed to be "one- offs", irregular production. With that in mind, marking a Sonnar lens "Leica Sonnar" could have meant it was for a Leica. Amedeo adapters are marked "Contax-Leica" and "Nikon-Leica". The markings on the lens- "Leica Sonnar" might be that the indexed cam is set for Leica, rather than the Russian standard.
Five "One-Offs" that I worked on over 10 years ago, including the one on the left that was marked "5cm" but was actually closer to a 58mm lens.
The second from the right: did not have a distance scale engraved in the focus ring. None of them worked properly, some were glued into place. All- usable after improvising some fix, including polishing down the RF cam on the one glued into place.
One of them had the proper SN stamped into the interior of the focus mount.
Thanks Brian for an, as always, interesting and useful reply. Your statement "...marking a Sonnar lens "Leica Sonnar" could have meant it was for a Leica. " holds out totally in the last picture of this thread where a similar lens says "für Leica":