I am not quite sure what 'Gaines' are in this context, but an extra 4 Francs buys you deluxe versions of them in Duralumin or Cadmium plated steel.

This low-res, deliberately smudged, scan is from the web site of the excellent Musée d'Art et d'Industrie in St-Étienne.

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• Publisher: L'Industrie des Cycles et Automobiles
• Country: France
• Date: January 1935
• Derailleur brands: Cyclo
• Derailleurs: Le Cyclo