fixer Isn't that the Campagnolo Cambio Corsa? It's not fixed, it's not even ss.
Could be Simplex - depends when the photo was taken..
"Fausto Coppi was paid a considerable sum to switch from Campagnolo's Cambio Corsa to Simplex derailleurs.
Coppi went on to win the 1947 Tour de France using Simplex equipment. He would go back to using Campagnolo equipment to win the 1950 Paris-Roubaix." http://www.theracingbicycle.com/Tullio.html
Could be Simplex - depends when the photo was taken..
"Fausto Coppi was paid a considerable sum to switch from Campagnolo's Cambio Corsa to Simplex derailleurs.
Coppi went on to win the 1947 Tour de France using Simplex equipment. He would go back to using Campagnolo equipment to win the 1950 Paris-Roubaix."
http://www.theracingbicycle.com/Tullio.html