"It's in too good a condition to be, but it sort of looks like the acid ampoules the British used on limpet mines and other demolition munitions during WW2.They worked by being put into the detonation system, then being crushed. The acid would eat through copper wire (different thickness of wire slowed down or sped up the time). Once the wire split, the detonator would trigger and bang.The ones I saw, admittedly years and years ago, were a bit flatter? I saw them in a museum in Portsmouth back when I was at college - 20+yrs ago. They came in a impact resistant case.Can't be, but looks similar."