In light of the above text printed on this historical piece of inner fuselage skin, it is most likely that this piece was located at the rear of the aircraft’s inner fuselage, close to the exit door. This was most likely the location where the lever was for the "para pack release" was situated. Para packs (parachute packages) were supply packages, most of time containing ammunition or rations attached to the belly of the aircraft, that would be dropped above the drop-zone. After the supply packs were dropped, by using a salvo release switch in the cockpit or a manual salvo handle in the back compartment of the aircraft, the parachute of a supply pack would unfold to safely descent the package on to the drop-zone. The image below shows the system onboard of a C-47 and the para-packs attached underneath the aircraft.