This photo is of a Ratier, it's a 600 cc French bike, based on the 600 BMW of the late 50s/early 60s. These were built for only a few years. They were based on BMW technology, using some parts made under license and I believe one or two, like crankshafts, provided by BMW Munich (could be wrong about that). By all accounts they were quite an improvement over the BMW - different frame and forks giving better roadholding, about the same top speed but more bottom end grunt, allowing very slow riding (presidential motocades...).
And that's the clue: Ratier had no dealer network and virtually the whole production run went to official bodies in France, mainly police.
The bikes were sold off surplus in the 1960s or maybe early 70s. The company still exists, making aerospace components, but refuses to have anything to do with its motorcycles or their present owners. There is a Ratier club in France which provides a small-scale spare parts service.
Photo is of a Ratier parked outside Orleans train station in summer 1967. I mean the old Orleans, not the New one!
