Very much so. Batifoulier & Collas built 2,500 frames per year for the likes of Puch, Wolhauser and apparently Calmus.

I would put the build date of your frame in the early eighties, because of the top tube cable guides and the shifter cable routing under the BB shell. And if the above information on when Jean started building his own frames is correct, it won't be later than 1983.

The 600 EX could be original to the bike, and in that case the Shimano date codes on the parts could yield some more insight.