Inside the Chieftain's Hatch" AC 1 Sentinel

The_Chieftain: Fascinating, Bonesaw. Out of interest, what are your sources? I'm not familiar with Mr Mellor's work, incidentally.   I'm ahead of myself, but indeed the oval was visibly a hatch from the inside. It still has the unlocking mechanism. The cut-outs in the turret, however, have me baffled to this day.