The grunt tanks of Saunders shown in the manga.
The M4A3 was a M4A1 with a Ford GAA V8 engine, made by the Ford Motor Company.
The U.S. Army intelligence believed that the M4 Sherman was more than enough to win a war. But that time was 1940. When the majority of tanks were light tanks while medium tanks had only 2 inches of armor with 2 inch guns sometimes with no radios. The Sherman had 3 inches of armor and a 2.99 inch guns and wireless radios. It was easy to see why the Sherman was superior.
The M4A3 arrived in 1944 from Normandy to Belgium. The Sherman's combat in 1941 Africa was superb in defeating the menacing Panzer III's. The Panzer IV fared the same but the F2 and H models held firm. Some unmet Stug III F/8's were also a challenge that was beaten by the older tank design. The advantage that the Sherman had that no other tanks had was a gun gyroscopic stabilizer that stabilized it's main gun and optics during movement.