This magnificent object is Francis Charvin's first Le Lautaret derailleur, named after the intimidating 2058m pass in the French Alps that has featured in the Tour de France so many times.

The patent describing this design dates from 1930, but the earliest adverts date from 1931. I have speculatively decided that it was introduced in 1930.

The design includes:

• a very distinctive symmetrical cage with heavily offset pulley wheels
• a massive central cylinder housing the sliding rod and spring assembly
• an internal spring to provide chain tension, which is unusual for the time.

• Derailleur brands: Charvin
• Country: France
• Date of introduction: 1930?
• Date of this example: unknown
• Model no.: unknown
• Weight: 419g
• Maximum cog: 26 teeth?
• Total capacity: 12 teeth?
• Pulley centre to centre: 52mm
• Index compatibility: friction
• Chain width: 1/8”
• Logic: low normal
• B pivot: none
• P pivot: sprung
• Materials: steel