Krupp was a steel maker in Essen, Germany. Krupp also got into the armaments business, making artillery and other weapons from the late 1800's through WWII. During WWII, the Krupp facilities were bombed mercilessly, but still only about 1/3 of the equipment was destroyed. As part of Germany's reconciliation with the eastern European countries at the end of WWII, about half of the undamaged equipment at Krupp was sent by train to the eastern block. Krupp continued in business after the war as a commercial steel maker.

The word "Krupp" on barrels does not indicate any particular grade of steel, just that the steel came from the Krupp factory in Essen, Germany.