I photographed this M15 Combination Gun Mortar Carriage at the Fort Lewis Military Museum. This self-propelled anti-aircraft gun on a halftrack chassis was equipped with one M1 automatic 37mm gun and two water-cooled .50 caliber M2 Browning heavy machine guns. Other WWII halftracks include the M3 Halftrack (Autocar, Diamond T, White Motor Co.) and the M5 Halftrack (International Harvester). Specialty Half Track versions also include the M16 MGMC Half Track “Meat Chopper” with a mount of four guns.