This is a machined aluminum 'incendiary' grenade (it came in a zip-lock bag that was labelled 'incendiary'). I don't remember seeing this particular type of grenade in the movie, but it does have marks on it like it's been thrown at least once. It features a sliding safety mechanism and a spring-loaded safety lever that will actually fly away like on a real grenade. The grenade itself is a solid piece of aluminum.Here it is with the safety device lowered showing how the lever would come off.
