Thank you for viewing. This is a U.S. Military issue SDU-5/E LIGHT MARKER, DISTRESS. It is a distress signal light used by aircrew members, etc. The dedicated battery (BA-1574/U) and pouch shown in the image are included. I inserted the included battery and pressed the switch, but it did not flash. I am selling it as a junk item (no operational guarantee). I'm including two extra batteries, just in case, though I don't know if they will work. Please consider it for display or collection purposes.