This advert is the earliest mention that I have found of the classic Terrot Modèle HT 4 speed derailleur system. The suggested gear ratios equate to 79”, 65”, 48” and 37”.

(Source gallica.bnf.fr/ Bibliothèque nationale de France)

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• Publisher: T.C.F. Revue Mensuelle
• Country: France
• Date: March 1912
• Derailleur brands: Terrot
• Derailleurs: Terrot Modèle HT