Kriegsmarine U-Boat flak gun sights

[Jesse]

Hallo Gents, I am curious about u-boat flak gun sights and am looking for some help. I imagine that there would be three different types ? One for the 88 and two others for the later period guns in the wintergardens perhaps? Most that I?ve seen have a type of view finder that one?s face would be pressed up against. Is anyone aware of a type that has a large circular-direct line sight? Would these have been used on a U-Boat and if not what type of artilary peice might they be specific too?

I?m interested really in what these sight looked like. Any photos or links too would be greatly appreciated. Thanks alot for any help. - Jesse