This is the fourth in a series of Alfa patents for pull-chain derailleurs that feature basically the same hanger plate, cable routing and derailleur body. For this final version of the design, Nicholás Arregui Gallastegui faithfully copies the slightly curved body and sprung double pulley cage of the 1946 Simplex Champion du Monde 46.

• Publisher: Oficina Española de Patentes y Marcas
• Inventor: Nicholás Arregui Gallastegui
• Country: Spain
• Date: Spanish application filed June 1948
• Derailleur brands: Alfa possibly intended to be marketed as Simplex
• Derailleurs: unknown