From an e-mail to Ric:
From: DANIEL C.
Date: June 4, 2013
I note that you folks are collating a series of Sextant Manufacturer's Serial Numbers against Naval Observatory Certification Numbers. In my possession is a Keuffel and Esser sextant, model #5227 that was manufactured about 1915/16 with K & E serial number 31475.
The box is matching to the sextant.
The Naval Observatory number is found on a shield that is inletted into the outside lid of the box, as well as being engraved on the arc of the sextant itself, and that N.O. is 616.
There is also a "Certificate of Inspection" U.S. Naval Observatory card in the box with the correct mfg S.N. and N.O. of 616 dated 9/29/41.
There was an earlier Naval Observatory "Cert" card that had been glued inside the lid, but there is no written information left on its remains, and only just enough paper and printing to tell with certainty that is what it was. So this confirms that it had been "Certified" by the Naval Observatory at a much earlier date, most certainly in the "teens" when it was still quite new, but sadly the actual date of that earlier inspection, and any of its results. have been lost to us.
I hope you find this information of some use to you in your wonderful quest!