At our last house I found a spent bullet and a fired case both dug up in the garden at different times, and at opposite ends of our long plot.
I thought for years that the case, with its DM 1943 head stamp would be German (D=Deutsche?). However when I found them in a box of bits the other day, I googled the headstamp and it is American, Des Moines.
Although unrelated, they are both from a 0.5" Browning, one of the most common Allied aerial machine gun in use later in the war.