Comparing: E 50 Ausf. M vs. 121

The German Army demanded that the E-series tanks had transmissions positioned in the rear. However, the E 50 and E 75 tanks used the Tiger II engine-transmission compartment, which made rear placement of the transmission impossible. The E 50 Ausf. M tank was a redesign of the E 50 project with the transmission placed in the rear.

Development began in 1962 on a new medium tank based on the Type 59. The new tank was expected to feature improvements in firepower and armor protection. However, the project was canceled shortly after. Some technical innovations were applied later, in the development of the Type 69 tank. All 121 tank prototypes were destroyed during Chinese nuclear weapon testing.