Back to the Picture of the King Tiger which was identified in the most futile of fashions...
it's a Porsche turret, opposed to the Henschel turret that saw the majority of the production. The difference is that the front of the Porsche turret is rounded, and the Commander's Cupola bulges out to the side a bit. Designers were worried that the rounded turret would deflect rounds on to the top of the Driver's compartment