In my collection I have 15 period scoped rifles that included Kahles, Oigee, Zeiss, and Hensoldt. The Oigee is equal to any of these. The fisheye you describe leads me to believe that one of the small internal lenses is incorrectly installed. It may have been taken apart at some point in it's history and not put back together the right way. I don't know who is currently refurbishing these vintage scopes.