This is not a Simplex Tour de France, but a Simplex Junior 4D. The Junior 4D was a derailleur designed for two speed children’s bikes which mounted directly onto the end of the wheel axle, predating the Shimano Saint (M800) (designed for somewhat larger children) by the best part of half a century.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Lucien Juy
• Country: France
• Date: French application February 1957
• Derailleur brands: Simplex
• Derailleurs: Simplex Junior 4D