Shell Casing from WW1

"This shell casing was brought home to Cork in 1918 by our great grandmother. She had gone to France to work as a nanny in 1913 and was forced to remain there when the First World War broke out. In 1917 she walked out onto a battlefield in Rubay once the battle was over and found this and kept it. It was passed down to our grandmother and then to her son (our father). "