These are terrible scans (courtesy of the French Patent Office) of a slightly strange document (for example you could think that the spring is shown pointing in the wrong direction).

However they describe an interesting design for a fork type derailleur with a built in tension arm. This Charvin model was known as the GRI-GRI Course. Frank Berto suggests that this was produced in 1936.

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• Publisher: L’Institut national de la propriété industrielle
• Inventor: Francis Charvin
• Country: France
• Date: French application December 1935
• Derailleur brands: Charvin
• Derailleurs: Charvin GRI-GRI Course