This addition to French Patent # 669,030, dated 1934, describes what Frank Berto refers to as the 1935 three speed version of the Simplex Champion de France. (Irritatingly, the derailleur that Frank Berto describes as the 1934 two speed version of the Champion de France is described in French Patent # 739,662 dating from 1932. Simplex history is never simple.)
This particular three speed Simplex Champion de France acquired an extravagantly cut away pulley cage/chain guide and a curious wing bolt for attaching the pulley wheel - both of which bear little resemblance to anything that Simplex produced before or since.
This derailleur does show one very significant innovation that lives on in the majority of derailleurs produced today. This is the humble hanger plate appearing here in a recognisable form for the very first time.