One more history lesson.
The first great Italian derailleur was the Vittoria Margherita. Dominated from 1930-1940.
The second great Italian derailleur was the Campagnolo Cambio Corsa. Dominated from 1940-1950. Although the Simplex Tour de France was probably used more post war.
The third great Italian derailleur was the Campagnolo Gran Sport. Dominated from 1951-now. I say until now because is was the first commercially accepted parallelogram derailleur and all of today’s derailleurs that followed are just a derivative. The first parallelogram derailleur was made by Nivex in 1938. Never caught on.
VM
_MG_9137 by iabisdb, on Flickr
Cambio Corsa
Pecorari 042 by iabisdb, on Flickr
Gran Sport
Cinelli_Model_B 095 by iabisdb, on Flickr