WWII USAAF ethocel thermoformable water bladder

Rare genuine WWII USAAF ethocel thermoformable water bladder. These water pockets were surely used by the first waves but also by the airborne troops as evidenced by the photo below of a glider from the 101st Airborne. It closed with a screw clamp system. Unknown piece, whose use is still unclear and which was used during D-Day in Normandy.