One time rare find!  From the Oak Savanna of Central Wisconsin these lights were made specifically for the Historic Baraboo Ammunition Plant by the Holophane Company, circa 1930s.  Thought to be explosion-proof, the glass is double cut with fine exterior horizontal lines and interior vertical lines that give it strength but in turn creates a subtle two-tone sparkle.  The threaded glass fits into a cast iron shade holder.  Also available in a flush mount.