Throughout WWII, many prototype tank designs never made it to the battlefield but the innovations developed during their gestation did make it into production as refinements to existing designs. 

Case in point is the T-23 prototype, a radical innovation with heavier armor, electric drive, new turret, and 76mm high velocity gun.  The T23 turret was later adapted to the Sherman tank and the lower hull eventually became the Pershing.  It was even a test bed for the HVSS suspension.  Though rejected for its complexity and excessive cost, the technology gained made it a crucial link in the evolution of US armor design.

I ask, what if?  I will build the T-23E4 derivative as if on combat trials just to have a vehicle no one else has.  There are drawings of this type in Honneycutt’s Pershing book and that is enough of a validation for me.  T-23 may have never seen combat but it will once I get my hands on it!  Besides, I have to do something with the spare Pershing I have, and all the spare Sherman parts.