M201 - mysterious tub / caisse mystérieux

The body tub below has no serial number and a curious hole in the bulkhead. Can anyone offer an explanation?

photos sent to me by Ken Chapman

The jeep was rebuilt at La Maltournée in December 1971 / January 1972 and remained in service until the late 1990s complete with a roll cage. It was also fitted with a reconditioned engine in the late 80s / early 90s and sold at auction in 1998 to RR Services in Kent.

Chris Arthey contacted me to say that his M201 which was rebuilt in 1976 has a tub with similar details to the one above and added 'If you look closer there are no drip points along the top of welded seam that run into the little gutter. My jeep also has no serial number stamped above the fuel filter. The toe board gussets are also different with round holes only. The door way support, which usually has three holes stamped into it, has none. There are also little weld points and welded seams in the bulk head behind the engine.'

These bodies appear to have been made for the French army presumably when stocks of original Hotchkiss bodies ran out. Surplus stock of these were sold at auction in the late 90s / early 00s and were available from dealers at the time but the purpose of the hole in the bulkhead remains a mystery for the moment. Does anyone else have a jeep tub like this?