Protractor, Aircraft Navigation Plotter, US Naval Observatory

This is a WWII-era Aircraft Navigational Protractor (aka Aircraft Plotter) Kit as used in navigator-crewed aircraft of the US Army and Navy. This particular protractor has a tag from the US Naval Observatory stamped 1945. It would be fitted to the navigators map table to plot and revised the aircraft's course. 

The kit appears to be complete. Included with the protractor machine itself are two steel rulers in cardboard sheaths which attach to the protractor, one measuring 12 inches long with markings in 32nds and 50ths of an inch, and one measuring 18 inches long with markings in 32nds and 40ths of an inch.  It also has an envelope containing wood screws for flange mounting on a map table. 

The wooden case measures ~ 4 inches tall, ~19 inches wide, and ~9 inches deep.  The protractor is in exceptional condition and all bands are intact and swivel as they should.  The case has 3 internal labels, a diagram, a materials list, and instructions on caring for the bands.  The case is labeled BK Elliot Company, who was a maker/distributor of drafting and surveying instruments and supplies, of which Vemco was the protractor maker.  The case hinges and clasps have some rust and the leather handle is missing, but otherwise the case is in very good condition given its age.