http://books.google.fi/books?id=gztL...ockpit&f=false
Check page 19 for a schematic of complete REVI gunsight in focke-wulf.
There is real life cockpit of real life Fw-190. Captured in 1945. Slightly damaged protective leather band, around instrument panel.
In WW2 the armored glass for aircraft canopys was always the best optical quality armored glass, which provided least amount of distortions. This causes available light towards the pilot's eyes to be of highest quality. This aids in spotting the enemy. That was the German theory of aircraft building for example.
Purpose of the gunsight was to provide good target picture to the enemy who you are shooting at. And also help in stadiametric rangefinding.
Perhaps an aircraft glass expert would be more knowledgeable when it comes to the differences and similarities between gunsight glass and optical armored glass canopy.