This is an example of a vintage piece of Trench Art. Trench art refers to items such as used shells & bullets casings artistically reformed by soldiers into other items.
They date from times in & around conflict, with the World War 1 era being particularly prolific as soldiers whiled away their hours in the trenches.
This piece is made from a bullet casing & formed into a sword shape. It was intended to be used as a letter opener.
It is of a good size & measures approximately 16.5 x 3 x 1 cm. The bullet is marked "18" for 1918.