These items were marked as German flares. They are made of aluminum except for the one on the right which is bakelite. Only markings on any of them are on the bakelite version, see photo. The bottoms of all the pieces are thinner than the main body which might explain it was designed to blow out when the flare was ignited. The fuzes seem to be of the german ZZ42-mechanism, but integrated in the body.
I have placed this one with the US mines as it seems obvious that it's American, but how was it used and which fuze did it held? It was recovered from a US training area together with M1 and M1A1 mines (trainers).