At US National Archives, College Park Maryland, there are 16 folders of prints for the Artillerie St-Chamond Tracteur Cuirasse De 90HP. I have attached the cover of one of them. I did not have time to go through them, but I have attached the loose St.-Chamond drawings that I found in the file box.
Found these on my last day of my week visit in late March 2020. I have just enough time to go through and document the British tank prints (passed on to David Fletcher) and the Fiat 2000 tank prints (passed onto the replica builders in Italy), well as some of the files that I was looking for.