JC (3rd style) derailleur

And this is the third JC model in this collection. The design started life as an Argentinian copy of a late 1970s Huret Eco - and then became co-opted into being a mountain bike gear. This appears to be a matter of fitting a long (75mm) pulley cage and, entertainingly, what appears to be a Centeron-type guide pulley with, perhaps, 2mm of sideways float. Does this floating pulley indicate that this is an indexed system? My thoughts are:

The Huret Eco was never designed to be an indexed system, as it has no single element of the geometry that is generally considered to be essential. My guess is that any indexing would be more a matter of faith than of anything useful in the material world.
Whether it was indexed or not, the Huret Eco design has its p-pivot concentric with its guide pulley - so lengthening the pulley cage does not increase the maximum sprocket that can be used. So a modest 28T is still your limit.

Some other features are rather similar, but not identical, to those for my second example of a JC derailleur:

The b-pivot bolt has a screwdriver head - which is still a bad idea .
The adjustment screws have large, 6mm, extravagantly domed heads.
The cable is clamped with an 10mm bolt - which is big.
In contrast, the pulleys are, again, charmingly petite 9 toothed items without dust covers.

It is, however, finished in a rather tacky, but possibly macho, black finish - for those rough, tough, mountain bike boys.

One, more sensible, feature of this derailleur is that it is designed to fit a Campagnolo (not a Huret) dropout.

As with all the JC derailleurs in this collection I have no real idea of the date of this product. I just made my best guess.