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.