After compiling his first star altitude curves that would simplify celestial
navigation aloft, P. V. H. Weems encouraged Bausch & Lomb to manufacture an improved model of the Bureau of Standards aircraft sextant for commercial use. This is one of those instruments. The National Bureau of Standards transferred it to the Smithsonian in 1957. The referenced patent is that issued to K. H. Beij in February 1929.
Ref: K. H. Beij, "Means for Determining Altitude," U.S. Patent