This is Adolphe André Laval's patent for his Laval Poiplum fork-type derailleur.

Note that:

• Adolphe André Laval made his patent application only 7 months after Oscar Egg applied for his first patent for a Super Champion fork-type design.
• The chain tensioning arm can be unlocked and relocked using a secondary lever.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Adolphe André Laval
• Country: France
• Date: Priority date December 1932
• Derailleur brands: Laval
• Derailleurs: Laval Poiplum