Maybe the problem is a language barrier - there certainly is an alphabetical one!!
It seems that nearly every FSU camera for sale on evil-bay is "rare". Even the Zorki-4, which was by far the longest in production, is often billed as "rare". I have (in some cases more than one) every model of Zorki from 1 to 6, except the 2 -- now that one is RARE!! It's also a good bit more expensive than the other models, except for the vaunted "FED-Zorki", which seems to be the rarest bird of all -- and the most expensive.
I have one Zorki-3 that came with an instruction book. Guess what - it's in Russian, which I am totally innocent of. It could be that the same thing works in reverse.