Over the years I have collected / downloaded numerous documents for my personal reference. Attached is one in French, concerning the snail drum chests, but I cannot recall where I downloaded it from, so if from this site, I apologise for posting again.
I spent six years of my youth, many years ago in the French Foreign Legion and a life time working in French speaking countries in Africa since, so I have a good understanding of French, but for those that don't, the pictures are also of value, I believe.
Having seen some good reproduction Thompson transit chests, produced by D&B militaria, or their supplier, over the years, indeed I bought one, once upon a time; I still have a doubt about this one. Never take an 'arms dealers' word at face value.