I think it's a Huret Challenger from what I recall of what they looked like, due to the black plastic upper insert on the cage.

By the way, if it is a Challenger, that was a mid-level derailleur, having dealt with Huret stuff many thousands of years ago, it did not perform well, not nearly as well as Suntour especially but any other Japanese derailleur, it was closer in performance to mid-level, and even some high-level European/Italian stuff of the day, kind of sloppy in the shifting performance. That Challenger was better than the Eco though, and it was very durable but the materials used to give it that durability meant it was heavy. I don't recall any issues with it in regards to stuff failing on it, which is why it's still on that bike! Just keep in mind that if you are experiencing sloppy or sluggish shifting, it's nothing that can be repaired, you could improve it a tad with more modern shifting cables though, and maybe improve it more than a tad. When I toyed with those derailleurs all we had was the old school cable, the new stuff wasn't around yet obviously, and since I know that upgrading my regular Shimano modern cables to DA 9000 cables made a noticeable improvement on my 105/Ultegra equipped bike, and the regular Shimano modern cables are light years ahead of the cables back then, so I would suspect that a set of modern cables should help the performance and the feel of the Huret Challenger...or whatever the model is.