Over half a million of these 2½ ton trucks were built between 1941 and 1945 in GM's Pontiac and Chevrolet plants. There were numerous variants - this one is an open cab CCKW, which, I think, means it is a 1941 design, has all-wheel drive, a conventional cab, and duplex rear axles !

Canon Digital Ixus V2, monochrome in Picasa.