[m1903a3]

Congratulations! There are only a few of us lucky enough to own one of these.

One minor point: Although they are often called "U-Boat" ammo boxes, there is no actual historic basis for that as far as I am able to ascertain.

From known labels we certainly know they were originally used for P.04 ammunition by the Imperial Navy, but it is most likely that they were used by Torpedo boats and Minesweepers as well as U-Boats. Those vessels all had the P.04 as the primary crew weapon, that is the weapon they trained on in basic training and they are all comparatively "wet" environments.