Noel Davis was a graduate of the U.S. Naval Academy who in 1922, after having received further degrees from the Navy’s aeronautical school at Pensacola and from Harvard Law School, was put in charge of all naval reserve flying. In February 1927, Davis and the otherwise unknown Lawrence Radford filed a patent application for an aircraft sextant with enclosed optics and an external divided scale. Davis died two months later, having crashed the plane in which he hoped to make the first non-stop flight across the Atlantic, from New York to Paris, and which he hoped to navigate "using a new sextant of his own invention."
The Davis-Radford sextant was manufactured by Keuffel & Esser, and advertised as the DARAD. The Navy Bureau of Aeronautics designated the original form the Mark II, Model 1, and a somewhat modified form as the Mark II, Model 2.
Ref: Lawrence Radford and Noel Davis, "Sextant," U.S. patent
T. C. Lonnquest, "Operation and Adjustment of the Davis-Radford
Octant," U.S. Navy, Bureau of Aeronautics, Technical Note No. 178 (Feb. 6, 1928).
T. C. Lonnquest, "Operation and Adjustment of the Mark II Model 2
Octant," U.S. Navy, Bureau of Aeronautics, Technical Note No. 207
(Nov. 22, 1929).
"Davis, Ocean Flier, Began as a Cowboy," New York Times
(April 17, 1927), p. 3.