Quote Originally Posted by BMbikerider View Post
Be aware that the Industar rangefinder ring does not always give accurate focussing with Canon Rangefinder cams (And Leica Cameras too). If you get one it would be best to expose a roll of film at close and distant focussing points to check if all is OK, before parting with a lot of cash or a guarantee you will get your money back. I don't know if they can be adjusted for better accuracy but somehow I doubt it.
They can be adjusted by shimming the optical block, but on a properly functioning 50/2.8 like the I-61 you will not notice the deviation between the Leica and Soviet standards, even wide open and close up. It really only shows up in those conditions with fast lenses like the Jupiter-3.

FWIW, Fedka says late 70s for the I-61, but does not indicate when the style change occurred. I suspect they were not concurrent.