Ammunition cans were made of metal and held various calibers of machine gun ammunition. The U.S. Army primarily used .30 caliber and .50 caliber for the Browning machine guns (M-1919 .30 cal and M-2 .50 cal). These workhorse MG's were mounted on just about everything. Jeeps, trucks, aircraft, ships and even carrier by Infantry soldiers. The metal cans were routinely policed up after a battle and reused. Supply units would repaint the cans, refill with belted ammunition and stenciled the outside of the can with the type, caliber and packing number. A slip with the same information was also included in the can. This was meant to help soldiers report any problems with the ammo back to the supply units.

I bought a lot of 12 ammo cans in 2003 to use for my .30 cal and reenacting. Under the protective liner on the bottom of the can I found this packing slip: