
Books are useful, for research. I have a few that are not yet in storage, which is why I was able to suggest the vehicle ID so quickly.
In fact Woj is likely more correct than I. The Lorraine Schlepper had an armoured compartment in the rear of the vehicle, into which was fitted either the artillery gun as suggested by Woj, or the antitank gun as I suggested.
The compartment is the same in each case: it is only the gun and relevant fittings such as shell stowage racks that differ.
Which made the vehicle easy to identify, because that particular conversion, relocating the engine to the center of the chassis, and building the armoured compartment in the rear of the chassis, was reasonably common on several dozen Lorraine Schleppers.
Once that is known, then identifying the compartment usually leads to identifying the vehicle itself.
Kind Regards, Uyraell.