You're probably right as during the first half of the 20c. many retailers bought-in frames, mainly from the St. Etienne area but not exclusively and painted them etc. with their own name head badge. I believe that the head badge on this bicycle refers to Boulin as "constructeur" with a mention of a gold medal ! We shall see, in due course.
Apparently there were 2500+ different French bicycle head badges in the early 1950's and shortly afterwards most of them disappeared.
There are dozens for sale usually on eBay France - look under "velo ancien plaques" if you're tempted.