Hello everyone. Brand new here and hoping someone can help me with some info. Just picked up a very nice but well-worn french WW2 backpack. I believe it is an M36, standard issue, one cargo compartment, two side pouches and large covering flap with what appear to be m1915 brown leather arm straps. My question concerns a large inner flap sewn into the lining of the ‘outer’ flap. What was it for/how was it used? I cannot see how it could contain anything or really protect anything. Does anyone have an idea how it was intended to be used? Sure appreciate any insights. Thanks, Nezvanov