T18 HMCTier 3, Self-propelled gun
A proposed 75 mm howitzer on the chassis of the M3 light tank. Developed by the Firestone Tire and Rubber Company in the fall of 1941. Two prototypes were ordered after the project was approved. The first vehicle was produced in May and underwent trials in June 1942 on the Aberdeen Proving Ground. The project was discontinued in favor of more promising designs.