This, rather fine, derailleur is somewhat similar to that depicted in the instructions document 'Notice de Montage du “SIMPLEX” Route 1934'. This example looks like a slightly later version of the mechanism depicted in these instructions. For this reason I have suggested that it is called 'Simplex Route 1935'.

Note that this derailleur:

• Has a bell crank that is designed to accept the solder nipple on the cable. Later Simplex bell-crank derailleurs have a cable clamp bolt, with the expectation that the solder nipple is at the lever.
• The component that holds the bell crank is a single brass piece. Later Simplex bell-crank derailleurs have their bell-cranks mounted on a steel band clamped around a brass cylinder.

• Derailleur brands: Simplex
• Categories: Simplex - bell-crank models
• Country: France
• Date of introduction: 1935?
• Date of this example: unknown
• Model no.: unknown
• Weight: 501g including chainstay mounting bracket, but excluding one screw from the bracket
• Maximum cog: 28 teeth?
• Total capacity: 28 teeth?
• Pulley centre to centre: 70mm
• Index compatibility: friction
• Chain width: 1/8”
• Logic: top normal
• B pivot: sprung
• P pivot: sprung
• Materials: steel with aluminium flanges on the tension pulley