Marx Battleground, Training Center, and Other Military Playset Pieces - Training Center Armored Car / Scout Car - Gray Wheels and Black Wheels - HP

Marx made a whole bunch of vehicles for their various playsets. The later vehicles were smaller in size and made of  soft plastic:

However, their first vehicles were quite large and made out of a hard plastic in various shades of olive green and drab. Marx made quite a few of these larger sized HP vehicles. The vehicles in the earliest playsets came with free rolling wheels, while some later playsets had vehicles with friction motors. In addition, some vehicles had black wheels, while others had gray. 

Marx's Scout Car appears to be based on the M8 Greyhound Scout Car (Light Armored Car) in use with American and British forces from 1943 until the end of the war. Per The On-Line Tank Museum 

"...M8 Greyhound was a small, 7.9 tonne American armored car with 6.4 mm to 25.4 mm of armor, only enough to protect against rifle caliber bullets, and armed with a 37 mm M6 main gun"

Courtesy The On-Line Tank Museum

Box art from the period does reflect the piece being referred to as an "Armored Car'', while the Sears Wishbook of the time does refer to it as a "Scout Car". So both names are appropriate for collector's. The  piece measures: 7" (17.78cm) L x 3.125" (7.93cm) W x 2.75" (6.98cm) H.

Ed

1951 Sears Wishbook extract only shows the scout car and a halftrack. As the years progressed, more and more vehicles would be added to the fleet.

Gray Wheels

The gray-wheeled Scout cars were included in the earliest Training Center playsets

Black Wheels