About this detail of the Tiger
The Tiger's hatches could all be locked from the inside with handles. The turret roof hatches, in addition, could be locked with padlocks and built-in locks from outside. For example, this is the lock on the cupola [1] of Bovington's Tiger "131". It requires an Allen key with an 8mm x 16mm oval head.
Tigers carried two of these keys, which I cannot depict in detail because I have not found any good images [3, see plate 58a] . The keys were originally kept in a small holder on the rear right inside wall of the turret, exactly above the smoke grenade trigger box. They are highlit in this diagram of the "flattened" turret wall. All of the neighbouring items of equipment are drawn.
You can see the holder, if not the keys, in the wreckage of Tiger 132 of s.Pz.Abt.501.
At about the 20th Tiger, an electric cable was removed from the upper turret wall. Equipment in this area remained almost unchanged, but it seems that the key holder was moved 20mm upward, because this is the layout that we find [2] in the surviving Tiger "712".
About the 56th Tiger, a change was made in the turret. Items were moved from the walls to a scaffold made of metal strips. The key holder was placed low down at the rear middle of the turret wall, between the flare boxes.
[1] Survey of Tiger 250122, at Bovington museum, by David Byrden