What an amazing "journey' this puzzle was.
Once we had established it was a circus bus, I fairly quickly found the two photos below of a Renault described on a "Pinder Enthusiast Site" as a ZPDF.
In all, I found 6 Pinder sites and perhaps another 6 just dealing with French circuses as well as 2 dealing with the Family Spiessert. In spite of all of this, I was unable to find any complete link to Circus Pinder or Spiessert, just this comparison photo which did not have the Pinder name on it.
However, given my interest in military transport vehicles 1935-1945, I found an absolute gold mine of photos of Mack, International, Marmon Herrington, Diamond T and Dodge trucks that were purchased as "war surplus" and used as tow trucks and for other duties by French circuses well into the 1960's. Three dozen photos and I am not finished yet.
I still have no photo of this bus with the Pinder name on it and multiple searches on the subject of Labourdette also failed to turn up any other photos of the bus. But, I am still happy with all the other materiel the search brought me.
Bill