A pdf file containing the Annual Reports of the Naval Observatory for 1919 to 1930 (minus 1921 and 1922?) can be downloaded
here Annual reports for various other years, before and after this period can be downloaded or at least viewed
here.
Much of these reports discuss the astronomical work of the Naval Observatory, but there is interesting information about the observatory’s eccentricity testing of sextants as well. From this information I came up with an estimate of about 4600 Naval Observatory numbers assigned to sextants between 1915 and 1919 (a key assumption being that, during the 1916-1920 period, every sextant given an eccentricity test had a USNO number, and every sextant was only tested for eccentricity once ). The sextant with N.O. number 1542 would seem to be have been issued during WWI. After 1923, it looks to me that very few if any new sextants were purchased the USN and few additional naval observatory numbers were assigned to sextants. I know I'm being vague about this, but I hope to get around to posting more on the N.O. numbers on another thread. Here I want to focus on what the USNO annual reports say about the fate of WWI era sextants, of which I think the sextant stamped with N.O. #1542, was one.
I was able to find three routes by which such sextants left the US Navy. I will bury the lede, so to speak, and list these from least interesting to most (you are now free to skip ahead):
1- During WWI, the Navy borrowed large numbers of instruments, from the public including sextants for shipboard use. These borrowed instruments were returned to their owners, who received certificates of appreciation. This is discussed on pages 3 and 12 of the fiscal year 1919 (FY19) annual report. I suspect that only a tiny fraction of the USN’s wartime inventory of sextants came from the public, so it seems unlike that sextant #1542 was one of them. All the same the USN appears to have taken care to keep track of these instruments and their owners, and if the borrowed sextants were given N.O. numbers, those sextant numbers might be in records pertaining to borrowed sextants, wherever they may be.
2- A possibly more significant discharge of sextants from the USN occurred in 1928. The USNO annual report for FY28 (page 15) then tells us that “A considerable amount of material reported sent to the naval yard, Washington, in the last annual report was found to be in excess of obsolete, and has been sold.” Records of transfer of navigational equipment from the USNO to the Washington navy yard in 1927, or of equipment sales by the Washington navy yard in 1928, would be interesting to obtain.
3- In terms of the Nikumaroro hypothesis, the third way that the annual reports tell us that sextants left the USN is the most interesting one. The FY19 report, page 3, tells us that “ Up to the date of the armistice, in November 1918, the personnel of the Naval Observatory was concentrated chiefly on supplying the compasses and compass equipment, navigational instruments, instruments for aviation, nautical almanacs, and time service, not only for a greatly increased Navy, but for the Shipping Board to supply its vessels with navigational equipment”. On Page 7 of the same report: “The continuing increase of the Navy up to the time of the armistice intensified the situation which existed during the previous year in regard to obtaining nautical instruments, and the observatory was also called upon to fill certain requests of the Army and Shipping Board for them”. The FY19 report tells us: “ By supplying the Shipping Board vessels with part of their navigational outfits the observatory has been able to dispose of what would have become a large surplus stock of instruments”.
The Shipping Board, as I understand it, was the government agency set up to build up the U.S. merchant fleet through a subordinate agency called the Emergency Fleet Corporation (EFC). It appears that a significant number of sextants stamped with USNO numbers may have gone to EFC-built merchant ships. What makes this interesting is that, according to the
Tighar Research Paper on Fred Noonan, Noonan served on U.S. merchant vessels during and after WWI. We are told in the research paper that “Noonan’s career as a merchant seaman is documented by US Shipping Board, Emergency Fleet Corporation records”. Apparently Tighar has these records (they are listed as reference 10 of the research paper). It would definitely be worthwhile to try to find out more about transfers of sextants from the USNO to the US Shipping Board/EFC, don’t you think? A partial list of Shipping Board merchant ships can be found
here.