Back to its roots - the B1 was originally proposed as an SPG and the turret later added :)
Originally 2 versions were proposed for the SPG - 1 with the 75mm and 1 with a 47mm AT gun instead.
3 of the 4 prototypes initially developed for the concept ( SRA, SRB, and FAHM) had machinegun turrets as well.
The 4 (including FHM without turret) were sort of combined into 3 more prototypes No’s 101 (Renault), 102 (FAHM but transferred to Renault), and 103 (FCM), with bits and pieces from all of them scattered throughout.
the final Char B1 that came out of all this was similarly a mix of various technologies, and hence was not called by the name of a single manufacturer.
The wiki article is interesting - Char B1 - Wikipedia