The scout car M2 featured external pintle mounts for its .30cal machine guns, and two of these can be seen above the rear wheel. This car has its removable canvas top installed. (Picture from Development of Armored Vehicles, volume II: Armored Cars, Scout Cars, and Personnel Carriers.)
In contrast to the earlier M2, the scout car M2A1 (later renamed M3) had a skate rail mounted even with the top of the armor. The layout of the side armor was changed from the earlier machine as well, and the glass windshield on this vehicle featured side wing panes and protruded to the edge of the armored flap above. The glass windshield folded forward when the armored flap was lowered. (Picture from Tank Data, volume 3.)
The machine guns around mounted on this vehicle. (Picture from Development of Armored Vehicles, volume II: Armored Cars, Scout Cars, and Personnel Carriers.)
Compared to the cars above, the wider body of the M3A1 is obvious. The top-hinged armored windshield cover is raised on this vehicle, and the glass panels can be contrasted to the earlier vehicle above. The canvas top is on, but rolled up at the sides and rear. The machine gun skate rail can be seen above the passenger door; note the padding to protect passengers. The box on the passenger running board housed the battery. The armored radiator louvres at the front of the vehicle were controlled by the driver, and the engine exhaust pipe can be see in front of the rear wheel.
This vehicle has its canvas top removed since it's a pleasant day. A .50cal M2HB machine gun is facing forward over the hood, and a .30cal M1917A1 machine gun faces out from each side of the passenger compartment.
This rear view showcases the water-cooled .30cal machine guns. Stowage for the machine gun tripods is visible on the rear plate and bumper.
A view into the passenger compartment from the driver's door is shown here. The tall radio installation can be seen behind the driver's seat, and details of the .30cal MG skate mount are visible towards the rear of the vehicle. The rail was lower when compared with the scout car M3, where the rail was even with the top of the armor.
The seating arrangements and internal stowage can be seen in this view. (Picture from TM 9-705 Scout Car M3A1.)
The driver's and front passenger's seats are shown here. The bottom of the cradle mount for the .50cal MG can be seen at the top of the image.
The driver's compartment is detailed here. The nomenclature is as follows: A. Trouble light receptacle. B. Stop light switch. C. Blackout and service lights switch. D. Dual fuel tank selector switch for fuel gage. E. Instrument cluster. F. Throttle control. G. Ignition switch. H. Starter motor switch. I. Speedometer. J. Heater switch. K. Dash light. L. Voltmeter. M. Screw. N. Map compartment door with key. O. Windshield wiper tube. P. Windshield wiper assembly. Q. Vehicle registration plate. R. Radiator shutter control lever. S. Fire extinguisher bracket. T. Heater. U. Voltmeter push switch. V. R. H. ventilator control. W. Choke. X. Transfer case shift lever. Y. Hand brake lever. Z. Transmission gearshift lever. AA. Accelerator pedal. BB. Spark. CC. Brake pedal. DD. Foot dimmer switch. EE. L. H. ventilator control. FF. Clutch pedal. GG. Horn button. HH. Gearshift instruction plate. (Picture from TM 9-705 Scout Car M3A1.)
This image shows the machine gun mount carriage M30. The carriage could be locked at any point on the rail and canted to compensate for the vehicle's position. An anticant device also accounted for the track's horizontal displacement. (Picture from TM 9-705 Scout Car M3A1.)
Details of the anti-ditching roller can be seen here.