The AN-M8, or M-8, flare pistol was developed by the Eureka Vacuum Cleaner Company and adopted by the U.S. Army Air Forces and the U.S. Navy Bureau of Aeronautics in July 1942. M-8s were produced throughout WWII and into the 1950s. The barrel has lugs for attachment to an M1 flare port that would have been issued with the gun but permanently installed on the fuselage of certain aircraft during the war.
The guns were often stored in their aircraft mount but were issued with a canvas pouch to hold flares that had a loose canvas holster, and they could also be used as a conventional flare pistol. The barrel hinges down for loading and removing flare cartridges. The right side of the frame is properly stamped with a triangle enclosing four letters, “US Property” and the designation of the pistol.
The upper letters M/S.W.C. stand for one of the two manufacturers of M-8s, the McNery Spring and Wire Company. This company and the Eureka Vacuum Cleaner Company together produced about 340,000 M-8s during WWII; this one is serial No. 307480 (stamped on the back strap) making it likely to have been made in 1944 or 1945. The frame is unfinished cast aluminum; the barrel is Parkerized steel.