This combat car M1, serial number 32, is topped by the early, D-shaped turret. The anti-aircraft machine gun mount can be seen on the turret's left rear. This vehicle is armed with a .50cal MG in the turret's left-side M15 mount, and .30cal MGs in the right side of the turret and in the M8 bow MG mount. The crossed sabre emblem of the Cavalry can be seen just above the turret pistol port. The siren is behind the barrel of the bow machine gun. (Picture from Development of Armored Vehicles, volume 1: Tanks.)
Pioneer tool stowage is visible on this side of the vehicle, and the drivers' doors and turret roof are open. The cylindrical engine exhaust is mounted on the rear fender, and on the rear of the sponson is an engine air filter. (Picture from Tank Data, vol. 2.)
This very early combat car retains the rounded engine cover and round turret. The turret roof is folded forward, and the semicircular vertical shield formed by the turret roof plates is visible. (Picture from FM 30-40 C1 Military Intelligence Identification of United States Armored Vehicles.)
A better view of the rounded engine cover is provided here, and the turret roof is again folded forward. The piping from the air cleaners immediately descends into the engine compartment, which was a characteristic of combat cars with gasoline radial engines. Taillights are just inboard of the engine exhausts on the rear fenders, and the antiaircraft machine gun is in the raised position in its elevator bracket mount. (Picture from Weapon Mounts for Secondary Armament.)
The antiaircraft elevator bracket is isolated in this image. This was the precursor of the bracket mount M20, with differences including the pintle clamp location, mounting pad details, and not having a finger lift cam in the position lock. (Picture from Weapon Mounts for Secondary Armament.)
The initial round turret can be contrasted here with the octagonal version made of flat plates. The motorcyclists help to illustrate the diminutive size of these machines. (Picture taken 1 Jul 1938 by E.O. Goldbeck; available from the Library of Congress.)
This M1A1 combat car showcases the octagonal turret fitted to later vehicles. The increased distance between the suspension bogies and the more rearward position of the idler are obvious when compared with the vehicle above. This combat car has all machine guns fitted, and all of the drivers' doors are open as well. The folding roof panels are positioned to provide protected vision for the turret crew. (Picture from Development of Armored Vehicles, volume 1: Tanks.)
The increased suspension spacing introduced on the combat car M1A1 is easily seen in the right-hand vehicles. The longer piping from the engine air filter stretching across the rear deck on the right combat car indicates that is is a diesel-engined M1A1E1. (Picture taken 1 Jul 1938 by E.O. Goldbeck; available from the Library of Congress.)
