Offering some night photos of this spooky triangle shade that appeared in vendor supply catalogs of the 1930's. The shade collapses flat, folding on a deliberate line through the middle of the owl. (It's a peculiar design decision that over time has usually reduced the quality of that particular pane). Original method for maintaining the expanded shape of the lantern is currently unknown by this blogger - (and information is welcome).
Note that the item (shown below in excerpt from an original 1937 catalog) is advertised as a die cut which is the industrial "cookie-cutter" process that made so many vintage holiday items, (and not just 2-D flat decor). See earlier blog entry from December 2014: Halloween Diecut Quiz.