History of the T6E1 Grizzly
An early prototype of the M4 Sherman medium tank. It was developed as a replacement for the M3 and inherited many of its systems and parts, such as the suspension, commander's cupola, and hatches on the sides. Work on the prototype for a tank with a cast hull finished on September 2, 1941. The tank was renamed and, after a few constructive changes, entered mass production as the M4 Sherman.