This is a Walter truck, manufactured by the Walter Motor Truck Co. while they were located in Ridgewood (Long Island), New York between 1935-1957. The company moved around New York State a bit, both before and after Ridgewood. It appears to be the standard "Traction Truck", although it could be the more specialized "Snow Fighter" used for plowing duty. It's very hard to date a late 40's to late 50's Walter from a picture, they didn't change much. This one looks like a typical late 40's-early 50's Walter. All of them were massive, powerful all-wheel-drive trucks used by many municipalities, especially here in the Northeast. I remember these trucks well from winters of my youth. Not much could stop them.