About this detail of the Tiger
The Tiger 1, as initially designed, used seven direct-vision blocks in the turret. There were five in the cupola and one in each side wall. Two boxes, each containing two spare blocks, were fixed in the turret.
This is a storage box for spare vision blocks, in the Bovington tank, before restoration  . Note the stencilling on the locking bar.
This is my CAD model of a box. It is made of sheet metal with no padding.
These are the dimensions of a box  .
The stowage in the Tiger's turret was rearranged several times. There are very few photographs of interiors and we may never know the full story. Several different arrangements for these boxes have been seen, and are shown in the following diagrams.
This arrangement is seen in tanks '712'  and '833' of S. Pz. Abt. 501  . The boxes are screwed to brackets welded to the inside wall, immediately to the right of the commander's seat. They are located up near the roof, probably because they have no lids and require no clearance above.
The tank's stowage was redesigned in December 1942  , possibly because the escape hatch was added. The Bovington vehicle was produced a few months later, with these boxes fixed in this arrangement  . The reason for moving them is apparently to put them on a web of metal strips that holds stowage items about 20mm clear of the wall. The two boxes are at slightly different heights.
This arrangement is drawn in the Turret Manual  for the turret with the 40mm roof. But it must have originated earlier, when the turret was redesigned with a new cupola. The new cupola uses periscopes, so the turret now requires only two glass blocks. There is only one box of spares, located near the loader.
In the final Tigers, as seen in the 'Saumur' vehicle  , stowage boxes were removed from the turret walls and replaced by open coaming on the turret ring. I don't know where the spare vision blocks, if any, were kept in these vehicles.(The latest version of this article)