The M26 was up-gunned by installing a more powerful 90 mm cannon. This tank was based on the first T26E1 tank. After trials at Aberdeen proving grounds, it was designated the T26E4 Pilot Prototype No.1. One tank was then shipped to Europe and was attached to the 3rd Armored Division. This tank was modified in the field with additional armor. The last picture show the tank proir to and after field mods, side-by-side.