:::buzz::: And the correct answer is....
The vehicle depicted is the T28E1.
This info is listed on the TANKS Web site.
T28, T28E1, M15, M15A1
This halftrack was armed with twin .50 cal MGs and a 37mm cannon.
Steve also wrote a book that had this model.
link More info. The vehicle was used in Korea also.

76th AAA used leftover WWII halftracks to fight. Jack R. Hayne, Capt, USA (Ret). of the 76th AAA in 1950-1951 is quoted as saying, "You must realize that we had the Quad 50s and 40mm guns mounted on ancient half-tracks that dated back to the WWII invasion of Leyte and Mindanao."
According to John W. Colburn of the 76th AAA in 1952-1953, the weapon shown is an early Multiple Gun Motor Carriage T28E1 with a 37mm automatic cannon and two water-cooled cal. .50 machine guns mounted beside and above the cannon and no armored shield around the gun. This was used in North Africa during the early days of WWII. When the armored shield was installed, the weapon was adopted as standard and designated as the Multiple Gun Motor Carriage M15. Later in WWII changes were made, most notably the water-cooled machine guns were replaced with heavy barreled air-cooled guns which were mounted slightly below and on either side of the cannon, and designated as the M15A1.
From this site:
http://kalanio.tripod.com/Howitwasa1b1x.htmlAhh....isn't our hobby facinating. :-)
Jim