The Mark II, Model 2 was designed by Noel Davis, modified by Keuffel &
Esser, and produced for the U.S. Navy. This example was the 3rd one made in 1929. The Naval Observatory transferred it to the Smithsonian in 1957.
Ref: T. C. Lonnquest, "Operation and Adjustment of the Mark II Model 2 Octant," Bureau of Aeronautics, Navy Department, Technical Note No. 207 (Nov. 22, 1929).
Lawrence Radford and Noel Davis, "Sextant," U.S. patent #1,743,979.