When the Tiger's turret was changed from the early to the late type, one of the improvements was in how the turret was locked during travel. An internal, late-model travel lock was introduced. The early turrets had been locked by a device mounted in the hull. To accomodate it, there were three slots cut in the walls of the early turrets.
The obsolete lock consisted of a steel plunger that was normally lowered below the level of the hull deck plate, but could be raised into one of the slots in order to lock the turret. The plunger was positioned at exactly 45 degrees left of forwards, outside the turret mounting flange. The slots were positioned as shown in the diagram above. Therefore, the early Tiger turret had exactly three locked positions; straight forward, straight rearward, and 14 degrees left of forward.
I cannot find any evidence of these covered slots on photos of the "Aberdeen" Tiger. Since it has the locking device in the hull, I assume that the very earliest turrets had round holes drilled entirely within the armour walls.
The slots were cut all the way through the turret armoured wall, and the resultant gap was protected by a rectangular armour plate.
At the rear position, however, the hinge plate for the escape hatch served to cover the gap almost completely and so there was no dedicated armoured plate.
This last diagram shows a profile of one of the front slots. It is embedded in the turret chin.
[1] Survey of vehicle 250122, Bovington, by David Byrden