With the Mark IV tank already done as a supply tank version, I wonder if anyone has done the St. Chamond version with the plated-over gun port yet. I did see a picture on page 20 of "French Tanks Of World War 1" by Steve Zagola.
Also wondered how the thing was marked and colored. The Mark IV tank actually said "SUPPLY" on it.
The Mark IV female I'm working on now is going to take some time to finish up.
I suppose that the caisson versions were not necessarily identical; the one pictured in my Zaloga book didn't have the big box on the top left, and common sense if nothing else suggests that there must have been field modifications of different sorts over time.