Only 100 were built, but the M12 Gun Motor Carriage played a significant role in supporting infantry in the push through France and pounding the fortifications of the Siegried Line. In Aachen, an M12 "bunker buster" let loose on the German commander's stronghold, causing him to lament "That's not fair." The gun was served by a crew of eight, and its onboard ammo supply was bolstered by the M30 carrier, which was an M12 hull with the cannon replaced by ammo storage.
The M12 below was photographed at Ft. Sill by Mike Riesmeyer. The museum says that "Adolph's Assassin" is the only surviving example of this AFV, but I believe there was one at Aberdeen, if I recall correctly.
In plastic, a very good M12 is offered by Academy. It was one of the first to offer the "straight arm" suspension. If you're particular about accuracy, take note that the track skids included in the kit may not be the ones used by the vehicles that appear on the decals. The early dome-like skid is available in the Tasca Sherman suspension sets.