VTG Jealousy Spy Glass Side-Angle Opera Viewer Turned Birch Wood & Solid Brass

VINTAGE JEALOUSY GLASS SIDE-ANGLE SPY GLASS VIEWER TURNED BIRCH WOOD & SOLID BRASS This is a neat little optical device which allows you to see with a diagonal perspective. Optical instruments like this were popular at the opera houses of the late 1700s where they were used to observe activities other than those on stage. While it looks as if you are focusing your attention on the performance, the ingenious spyglass you are holding is allowing you to watch the people to your right or left! The jealousy glass, also known as a polemescope, was invented by the German-Polish astronomer Johannes Hevelius in 1637. Hevelius believed his invention could have military uses, but the viewing angle was found to be too narrow. The item here is a 1989 reproduction by Van Cort and sold by The Museum Company. Two signed, solid brass end caps encase a dyed, laminated birch wood turning. A first surface mirror gives you a clear 45 degree view. The arrow will indicate which direction. Mirrors create the trickery. Take it to the opera ... to the theatre ... to a concert ... to the beach ... to parties ... to work. In original box from the The Museum Company Measures about 2.25" long and slightly over 1" across the round ends. A fun gift for the opera enthusiast, the woodworker, the unique gadget collector or kaleidoscope aficionado.