This is the earliest mention that I have found of the ‘new’ Boizot 5 speed derailleur. This system had, a very modern, 5 cogs on the rear multiple freewheel. It also incorporated a cunning ability for the front chainwheel to move sideways on the bottom bracket axle, in order to stop the chain getting too out of line. This is not as daft as it sounds as the chain width would be a relatively inflexible 1/8”.
I think that the 6 speed and 9 speed options advertised were the 3 speed Boizot Tri-direct used with a double or triple chainwheel respectively.
(Source gallica.bnf.fr/ Bibliothèque nationale de France)