I had a nice find from Russia while looking for some photo equipment: the Photo rangefinder DF (the DF probably stands for “Photographic Rangefinder”). It had a good price and it is just the right equipment for my Smena 8M. There was no much information about it except that it seems to be quite rare. According to fotoussr.ru it is a copy of the Smena rangefinder from GOMZ (State Optical and Mechanical Plant) produced at the MMZ (Minsk Mechanical Plant) for probably quite a limited time from 1957-1961.
I got it with a neat little leather case (instead of a plastic case), which was usually for the Leningrad Smena. So I checked if everything worked and it looked quite fine: the wheel worked well, the distant scale reaches from 1 meter to 10 / ∞ and is readable and the double image was clearly visible. However i saw the calibration was well off. Everything above 5m was just the same and the scale between 1m and 2m was always off about 0.5m. So i thought i could maybe recalibrate the rangefinder.
Boy, was this an adventure… There is no manual (at least i didn’t found one) and at first i used some try and error. That made everything worse and now i had a vertical misalignment too. Great… freshly brought and i managed to immediately broke it. Luckily i found a russian YouTube Tutorial where someone disassembled the Blik rangefinder and i thought maybe the design is not that far off. So i dissambled my new aquired rangefinder, used the far off späti as my ∞ point and tried my luck with the arrangement of the mirrors. It was still a bit try and error but i found the screws i had to adjust (although the YouTube video helped me to pinpoint them). Assembled everything back again and exchanged some screws that had the wear of time already.
I build up a small testing range and checked the settings with my SLR cameras and it seems to be neatly calibrated again and works like a charm. Cheers to Soviet repairability.