M8 HMC "Scott"

Beam me up, Scotty

Historical Overview:

In the late 1920s, the US Army introduced the 75 mm M1 Pack Howitzer into service. This lightweight weapon was intended to provide fire support to highly mobile units, such as paratroopers and marines, who could not easily transport heavy artillery. Even so, the US military wanted to create a self-propelled howitzer using the 75mm M1. Over several years, they would attempt to do so, but with little success, starting on the T1 Light tank, and some attempts on the M3 Stuart.

There were several major design flaws with previous projects; the howitzers were mounted with limited traverse, fully-enclosed superstructures provided minimal working space for the crew, and the barrel itself was vulnerable to damage. The T47 solved these problems by introducing a large, fully traversable, open-topped turret. Initially the M3 hull was considered, but the M5 was chosen as it was more capable and was entering production.

Source(s):
Tank Encylcopedia - 75mm HMC M8