From the accounts I've heard, only two complete hulls were made, a version 1 and a version 2. Several turrets were captured complete and in various stages of production. The russians took the V2 hull, and mated it with a V1 turret for evaluation (still not a complete prototype). Unsure about this, but I hear there was also some turrets fitted to be armed with the KwK 43 because of greater avaliability. As far as I know, the maus seeing combat is just a myth.