This is a strange and interesting device. It is a single pulley, two-speed, parallelogram derailleur. But it also appears to incorporate a chainlifting device - rather in the style of the 1897 Gradient.

A later design by the same inventor made it to market as the ORK? derailleur. I do not know if this, earlier, design ever got that far.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Karl Martin Alm
• Country: France
• Date: Priority date July 1940
• Derailleur brands: ORK?
• Derailleurs: unknown