With Trumpeter's E-100 turret, what are they trying to accomplish with the plate on the rear of it?

It doesn't seem to hing down for an escape hatch (no signs bolts or rivets) there seems to be some sort of circle plug (spent casing ejection? or feeding new ammunition in?).

My only idea at the moment is, it is an internally bolted plate that when removed allows the gun breach to be removed, since it can't go out thru the front plate? Sound resonable?

The King Tiger turret had a large rear hatch for dismounting the gun, which doubled as an escape hatch. Presumably, that is what is intended on the Trumpeter E-100 turret. Bear in mind that the turret in that kit is entirely fictional, being designed by modeler Mike Rinaldi for his own model, and copied by the manufacturer (who belatedly acknowledged his contribution).
Originally, the E-100 was intended to carry the Maus turret, as shown in the Dragon kit, but later the improved Maus II turret was substituted. This is all speculative, of course, since the whole project was canceled before any turrets were actually built. Cammett in the UK offers a very nice resin Maus II style turret for the E-100, if you want to upgrade the kit.

Thank you. I'll make a guess and the "bolted" on rear hatch is for removal of the gun assembly and not an escape hatch.

Gives me some lattitude when I begin this build for the addition of exquipment boxes mount to either side.