I think what you have is some WWI trench art. Looks German, dated 1914 ---1919. The side with the dates appears to have a German helmet, and crossed German hand grenades.
My guess is Brest is probably the guys name, or the location of where he was stationed. The type of engraving is crude, but used even by professionals. You take the graver and hold
it straight onto the metal, then rock back and forth, sort of in a twisting motion, and you cut those tracks. I know, because that's about all the engraving I can do, believe me, I've
built silver inlaid bits and spurs, and have tried to engrave the silver, and those turkey tracks are about the best I can do. Perhaps one of the guys from the UK can tell you more about
the side with the crown. You know what kind of metal it is?