Originally Posted by Gben
I don't believe that any Russian lens can be counted on as being an exact copy of a Zeiss lens. For instance a lot of Ebay auctions advertise Russian Jupiter wide-angle lenses as being Biogon copies, but that is laughable as they are of much cheaper construction with fewer and different elements.
As a matter of fact, the "Jupiter" lens production was set up by transporting the entire Zeiss Jena factories and their engineering and administrative staff to the USSR. The lenses started out almost exactly identical copies, with exactly the same number and type of elements, in exactly the same place - indeed, for the first two or three years they were mostly assembled from spares fabricated in Jena and Saalfeld. They diverged later, but optically to their improvement (as better glass and coatings became available) - the issue with the Soviets was with quality control, and even more so with a lack in innovation (the cameras and lenses essentially remained stuck at pre-war level, the decreasing demand for these outdated designs being countered by perpetually lowering the price and quality standards).
It however is rather unlikely that a group from a Soviet lens can be used to repair a Jena lens without having access to a fully equipped lens workshop - there are enough subtle differences between Jena lenses and later, affordable Jupiters that the results are likely to be underwhelming unless you have a autocollimator and the proper spacers.