We tend to think of Cyclo as one of the oldest and most venerable of the founding institutions of derailleur history - and quite rightly so. But in 1925 it was the new kid on the block - le dernier né des dérailleurs.
The Le Cyclo derailleur is advertised here in 2 and 3 speed variants (allowing 4 and 6 speeds with a double chainwheel). It had been available at least since 1924, as it was used with some success in the 1924 Semaine du Dauphiné.
(Source gallica.bnf.fr/ Bibliothèque nationale de France)