I also think you are looking at a matching left and right pair of inspection covers from the WWII era.
They most likely came from a German (my pick since I agree with MiTasol's comment) or Allied aircraft. You can see they were hinged at the bottom and secured by quick-release fasteners at the top and sides (used by both sides in the war). The left piece even has its original fabric anti-vibration tape still attached (widely used in WWII).
If you want to pin down the exact aircraft model, try shining a flashlight at a flat angle across the metal inside the edges—you could get lucky and find a stamped part number that will tell you exactly which aircraft they flew on. Also, sometimes simply measuring the tape width or fastener spacing can reveal if it was built using inches (Allied) or millimeters (German).