The T.C.F. decided to encourage the use of gear systems, that allowed the gear ratio to be changed while riding, in the Tour de France. To this end, in 1923, it donated a prize of 1,000 francs for the first rider to use such a suystem and 500 for the manufacturer of the winning machine. These prizes were won by a M. Biancho using a Boizot derailleur..
(Source gallica.bnf.fr/ Bibliothèque nationale de France)