Actually I too read a lot about lack of coherence between J12 and canon P checked it sold my old silver Jupiter. Soon on several occasions I found canon P woth J12, the only difference was it was later, black version last week I tried black J12 on my canon P and it was ok. s/n suggested it was from early seventies.
Tried the Industar-50
I have just tried to fit a collapsible Industar-50 on my Bessa-L, and, in the beginning it seems fine, excepted the dreadful facts that :
- it cannot be fully screwed, because the rear of the distance lever came in contact with the body (there is a little screw, back of the lock button), and simply scratchs it.
- it *must NOT* be collapsed, because the Industar locking bayonet come in contact with the Bessa baffling (not the shutter, thankfully).
It's a pity, since this lens gives very nice results, with his original camera, which is a Mir Rangefinder (a Zorki avatar).
Maybe this warning maybe useful to someone,