This was made after Carbonara filed his patent application in 1931 and before
the patent was issued in August 1934. It is identical to the original Model 342,
but here the eyepiece rotates around a vertical axis so that sights can easily
be taken in any direction. The U.S. Naval Observatory transferred it to the
Smithsonian in 1948.
Ref: "Recent Developments in Pioneer Aircraft Instruments," Aviation Engineering 7 (Oct. 1932): 16-17.
Pioneer Instrument Company, Aircraft Octant Mark III - Model 3 (Brooklyn, N.Y., n.d.).
Victor E. Carbonara, "Navigating Instrument," U.S. patent
Victor E. Carbonara, "Sextant," U.S. design patent #85,912.