Armored Car M1.
The armored car M1 had three axles, but only the rear two were driven. The spare wheel mounted on each side could turn freely, and would help the car from becoming ditched. The armored windshields are in place in this view, and later cars had flatter, less bullet-shaped headlights. The turret actually had a pyramidal top, although the lighting in this image makes it had to see. The car had a pistol port in the rear plate as well. (Picture from Development of Armored Vehicles, volume II: Armored Cars, Scout Cars, and Personnel Carriers.)
The top of the turret is more easily seen in this wider view. The armor flaps around the crew compartment are closed, contrasting to the image above. A shield through which both machine guns barrels protruded was clamped to the barrel of the .50 caliber. (Picture from Weapon Mounts for Secondary Armament.)
Further details can be seen in this image of vehicles belonging to the 7th Cavalry Brigade (Mechanized), in which fully 25% of the armored car M1's production run is visible. The rear fenders are used for stowage, and the armored louvres for the engine radiator are closed. The later headlight variant is present on all of these cars, and the folding armored windshields are in place. The passenger doors are open, along with the viewing slot in each one. The driver had a larger side armored flap, and these can be seen raised on the far sides of the cars. (Picture taken 1 Jul 1938 by E.O. Goldbeck; available from the Library of Congress.)
In 1935, the weapons were modified so that a single .50 caliber machine gun was mounted in the turret, and brackets were attached around the turret roof for mounting antiaircraft machine guns. (Picture from Weapon Mounts for Secondary Armament.)
The interior of the 1935-pattern turret is seen in this image, with the gun mount's shoulder rest on prominent display. (Picture from Weapon Mounts for Secondary Armament.)
