This instrument was developed at the Royal Aircraft Establishment around the time of World War I, and still in use during World War II. Lionel Burton Booth and William Sidney Smith, both of the R.A.E. obtained a British patent for the spherical bubble chamber, its key element, in 1919. The U.S. National Bureau of Standards tested a MK V in the early 1920s–perhaps this very one–and then developed a remarkably similar instrument.
Ref: K. H. Beij, "Astronomical Methods in Aerial Navigation," Report of the National Advisory Committee for Aeronautics 198 (1924), pp. 16-18.
Peter Ifland, Taking the Stars (Newport News, 1998), pp. 165-167.
