Cambio Benato was a derailleur produced by Angelo Gino Benato of Carpi, near Modena, Italy. The patent for the derailleur dates from 1938. The derailleur, itself, is a 'flipper' type device rather reminiscent of a Vittoria of the time. Somewhat strangely, it can be mounted below or above the chainstay - giving the choice of changing while pedalling forwards or changing while back-pedalling. Why anyone would chose the back-pedalling option is lost on me.