Contarex/Contaflex film back cross-compatibility

For those in the know: are Contarex/Contaflex film backs cross-compatible?

As they look almost the same I'm not sure. Looking for Contaflex ones, but now just came across one that is said to be for both, yet there is a pin protruding on the take spool side that I do not see on others, which suggests to me it might be specfically for Contarex and won't fit Contaflex.

Well, I have answered my own question, Film magazines are indeed cross-compatible between Contarex & Contaflex. I don't know what the pin mentioned is for, and some backs do NOT have it in place for sure. But I have the Contaflex Super BC and one of these (just dug it up) and it does have the pin. Looks like it may be controlling frame counter on the Contarex (does not appear to do anything on Contaflex but there is a recess below advance lever that accepts that protrusion. At least on Super BC with magazine on, frame counter on top advances along with one on magazines bottom.

So my question is answered, just now am wondering what this pin is for.

Have to chime in with "not all Contaflexes". I have interchangeable backs for a C-flex Prima (interchangeable Pantar front elements, not whole lenses) and they are way too small to fit on a C-rex ("C-rex", now there's an appropriate nickname for the Contarex-- a magnificent dinosaur, the apex predator of its time!).

nosmok said:

Have to chime in with "not all Contaflexes". I have interchangeable backs for a C-flex Prima (interchangeable Pantar front elements, not whole lenses) and they are way too small to fit on a C-rex ("C-rex", now there's an appropriate nickname for the Contarex-- a magnificent dinosaur, the apex predator of its time!).

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Well, true, I believe the Contaflex that had film back option was Super B and BC + Contarex. Earlier Contaflexes with no meter on prism's front did not.