Unfortunately there is no image on this registered design - but I believe that it relates to a Simplex Prestige Cadet of some type. The description specifies that it relates to a derailleur designed for children.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Lucien Charles Hippolyte Juy
• Country: France
• Date: French application October 1964
• Derailleur brands: Simplex
• Derailleurs: Simplex Prestige Cadet of some type