This is the first of Charles Jeanmot’s JIC derailleur patents - and I have to say that I don’t quite understand how his cunning device is supposed to work. But this 1932 derailleur design is recognisable as that of a discrete bicycle component that attaches at the rear dropout, is operated by a cable and contains springs and a chain-tensioning pulley wheel.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Charles-Jules Jeanmot
• Country: France
• Date: French application March 1932
• Derailleur brands: JIC
• Derailleurs: unknown JIC model