As single-pulley derailleurs go, this is a classy little number. It is very light, has a rather well crafted and usefully rigid arm and all its small parts are accurately made and pleasantly finished. Best of all, it has top-normal logic. The cable feeds down the inside of the arm, around a roller and out to a clamp bolt on the outside end of the sliding rod.
One end of the main spring is hooked around a set-screw that can be screwed into one of two holes in the sliding rod - depending on whether the derailleur is to be used with a 3 or 4 speed freewheel. The set-screw slides in a slot in the arm that provides a kind of rudimentary limit on the range of movement.
The Vittoria Giuseppina was a much neater device than a pre-war Simplex Champion du Monde, but was not really competitive with the twin pulley designs that were just hitting the post-war market.