The M6
The M6 Heavy Tank was designed and produced in small numbers during World War II, but never saw combat. By 1942, three prototypes were built by the Baldwin Locomotive Works. The prototypes differed by power plant, transmission and hull assembly method - one had welded hull and two cast hull.
However by the time the M6 was ready for production, the Armored Corps had lost interest in the project. The advantages the M6 offered over medium tanks were offset partly by the shortcomings of the design. By the end of 1942, the Armored Corps were sure that the new M4 Sherman gave adequate solution for the present and the near future.