This icon was a supertest leak.
The in-game description was also leaked: A variant of the M4 medium tank with angled hull and turret. It was developed by the Detroit Arsenal in August 1942. The changes were intended to improve the tank’s protection without increasing weight or degrading other technical characteristics. Existed only in blueprints.
This tank has almost no imformation of it exept for this scemantic:http://www.tankinfo.ru/Country/USA/1/medium/M4/images/M4_IP.jpg