This is the first Pioneer Model 342 (Navy designation Mark 3, Model 1) ever
made, and the first one made in 1931. It is compact and light; its optical train
uses prisms rather than mirrors; the bubble chamber is placed in the optical
path; and the dial is illuminated with radium paint, thus obviating the need for
battery and electric light. The National Bureau of Standards transferred it to
the Smithsonian in 1957.
Ref: "Recent Developments in Pioneer Aircraft Instruments," Aviation Engineering 7 (Oct. 1932): 16-17.
Victor E. Carbonara, "Navigating Instrument," U.S. patent
Victor E. Carbonara, "Sextant," U.S. design patent #85,912.