FWIW, someone posted here a Russian 1970 lens catalog a long time ago. I can't find the thread now, but looked at my download (my Russian is nil but I can recognize the Cyrillic characters).
The Industar-50 f/3.5 is listed in p.79 of this catalog as a single entry for both RF (Zorki, Fed) and SLR (Zenit) cameras, showing the same optics for all of them. The manual shows external dimensions of both collapsible and rigid versions. The specs for the RF and SLR version are identical except for flange-to-film distances (28.8 and 45.2 mm respectively), nominal focal length (53mm and 50mm) and weight (112 g and 126g respectively).