As I mentioned on the FB post, the blanking plate over the unusued rear lamp aperture suggests an undelivered French contract machine. The earlier photo of a French bike clearly shows an opening on the left of the number plate....the off-side in France.
That last picture is interesting, the "40" serial on the tank seems to be on a roundish shaped Signals? backing, could it be an Anti Aircraft Command machine, its said they used an ellipse shaped serial.
