My 'off the cuff' suggestion is obviously wrong
I have read that a few soldiers made momento's of the Zulu wars (a la 'trench art') and this seemed an ideal candidate. Well spotted Dennee, a pen case it is
the idea that it could be used as a cosh seems valid with those bulbous ends.
Still a very interesting object Tim, it is a shame the decoration has deteriated.... the clues it could have given you