Unusual Dated 1938 Trench Art Brass Ashtray

This solid brass small ashtray is clearly dated for 1938 on the base it also has other markings including P152 and 33, I think it is German in origin and is the central part of a much larger shell case which has been machined down and converted into the ashtray. It is heavy and comes in good condition although the rest for the cigarette looks out of shape, it measures just under two inches in diameter.