About this detail of the Tiger
Vision in the early Tiger 1 was directly through blocks of armoured glass. These were expected to shatter during combat and so they were removable, with spare units being stored within the tank.
The same type of vision block was used in the commander's cupola and the turret side vision ports.
The unit had a sealed shell of 2mm metal enclosing five sheets of thick, greenish bulletproof glass. There was an internal rubber spacer and a thinner pane of glass on the crew member's side; I am not sure whether these were for waterproofing or splinter protection. The vehicle was designed to be submersible, and the outside of these blocks would have been in contact with water.
The dimensions of the block are given here.
It is interesting that the vision block for the driver, in the hull, was of exactly the same design except that it was 240mm wide instead of 150mm. Therefore, on the Porsche Typ 101 (and the very first Tiger which had no periscope) all vision blocks were of essentially the same type.
[1] Survey of Tiger 250122, at Bovington museum, by David Byrden
[2] DW to Tiger 1