French Patent # 799,054 - Charvin

French Patent 799,054 - Charvin GRI-GRI Course main image

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.