Found it: it was called an ectascope and there are diagrams here: https://www.minnpost.com/stroll/2015/09/seven-stories-down-u-building-serves-tribute-minnesot

Found it: it was called an ectascope and there are diagrams here: https://www.minnpost.com/stroll/2015/09/seven-stories-down-u-building-serves-tribute-minnesota-experimentalism https://www.minnpost.com/stroll/2015/09/seven-stories-down-u... Not a very good photo of what it looked like: http://blogimg.goo.ne.jp/user_image/6e/29/0553c64f5a894a9391a29158d93d772e.jpg http://blogimg.goo.ne.jp/user_image/6e/29/0553c64f5a894a9391...