Gnome et Rhone AX2 Episode: 2
Gnome et Rhone AX2, 800cc.
Terrot JSS350 Episode: 2
French? Dijonnaise de chez Terrot, même!
I think this is a civilian model that has been commandeered by the military, who would chrome the tank on a military vehicle? Terrot JSS 350
BSA M20 Episode: 2
Wikipedia says that there were different versions producted for military purposes, production of them started ca. 1939, while the overall model was introduced in 1937. https://en.wikipedia.org/wiki/BSA_M20
BMW R12 Episode: 4
Please set year to 1935.