This is a Sachs-Huret Rival ARIS emblazoned with the word 'approved' and Galli's rooster symbol ('gallo' is the Italian for 'rooster'). Galli included this derailleur in some of its mid-range groupsets in the late 1980s.
The Sachs-Huret Rival ARIS is a presentable, solidly constructed and reasonably effective unit. It has its cable clamp bolt mounted on a sprung arm - to give what Shimano called a 'light action'.
In fact, compared to a Shimano Light Action derailleur of the time, the Sachs-Huret Rival ARIS was just slightly later to market, just slightly more expensive, just slightly heavier and indexed with just slightly less accuracy. It's cruel to say so, but it was also just slightly uglier.
It's tough competing against a highly capable, 800 pound, gorilla like Shimano.
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