I just found this:
The Kinon protection block.
The Kinon bulletproof glass block is typical for the time and was used as the primary viewing device during relatively safe periods of operation. The holder and outside armored flap is called a Fahrerseh Klappe50 and when in combat the outside armored cover was closed over the glass block by the large handles.
Once the Klappe50 was closed, the driver's KFF binocular optics were swung down into position over his glass block inside the hull. The binocular KFF was attached to the front armor plate above the viewing block and allowed a very restricted view through two small holes bored through the armor just above the armored cover.
This was the German Sturmgeschutz III version, and probably was used in other tanks at the time(?).
Did they use the same kind of thing in the allied tanks and later on in the heavy German tanks? Was there a distinct name as well? Does the Kinon come from the manufacturer´s name?
http://afvinteriors.hobbyvista.com/stug3/stug1.html