Found 50 cal shell on beach in Ocean City today

I didn't really find it but came across 2 women who where metal detecting. They've been dredging off shore to replenish the beach and all kinds of things are showing up. 
These 2 were working an area and found as many shells as they could carry. They gave me this shell and through a Google search found out that it was made in Saint Louis in 1943. 
Figure it was a result of practice off shore during the war. Pretty neat.