Andrew,
To expand on my last post here: Is there a grouping number around the A.E. box number and the Brandis number that may indicate a large government (Navy) purchase?
Is there a grouping number around the A.E. box and the Navy's Observatories recallabration inspection numbers?
Ted
Ted
These are good questions.
On a high level scale, what we've been able to discern is that the sextant box found on Nikumaroro with two numbers fits a pattern of sextants that were once part of the US Navy inventory, i.e. they have both a Manufacturer's serial number, and also a second number that we now know was issued by the USNO upon being submitted for calibration at the USNO. There is at best only a rough correlation between USNO calibration numbers and Brandis numbers, so it would appear that the Navy numbers were issued not upon purchase by the Navy, but upon submission to the USNO for calibration, which may have been significantly after purchase and induction into the Navy inventory. I imagine that new sextants were "calibrated" upon purchase and immediately sent to sea, and only after they'd been dinged and abused by swabees at sea and demonstrably off, were they then sent to be calibrated by the USNO. Hence the USNO sequence of numbers being out of synch with the Brandis numbers.
What has become apparent recently is that there is a point where Brandis apparently moved from manufacturing 7.5 inch radius instruments to 6.5 inch radius instruments, and it seems likely that the move to the smaller radius instrument corresponds with the Brandis contract from the Navy in October 1917 to provide 1000, later expanded to 2400, new sextants to the Navy.
We've been collecting info on sextants for quite some time, but we have not been recording the association of instrument radius with sextant numbers - just an example of information we could have collected if we'd known what to collect - but with the small sample I've been able to collect, the switch between 7.5 radius and 6.5 radius instruments seems to have occurred between Brandis serial numbers 3987 and 4297. All the instruments with serial numbers earlier than 3987 seem to be 7.5 inch radius units, and all the instruments after 4297 seem to be 6.5 inch radius instruments. If this is correct, then it illustrates that the theoretical sextant Brandis 3500 found on Gardner island was likely a 7.5 inch radius instrument, as it predates the switch by Brandis to a 6.5 inch frame.
All of this info on the differences in frames is something we did not know or recognize prior to this year. If we'd abandoned the collection of information last year due to boredom, and I know it can be a bit boring, we'd never have known this bit of information.
So to answer your question, I don't know that the numbers indicate a significant purchase of instruments in and around the theoretical AE instrument #3500. I rather think that the Navy purchase came later and was fulfilled with 6.5 inch instruments, so the AE theoretical instrument pre-dates the WWI purchase requisition of Oct 1917, and was already in the Navy inventory at the time of the war, but as others have postulated, not by much, as it may be that #3500 was manufactured during 1917. See the Blog on Ghost of Gardner Island that has been referred to earlier in this string.
What is important is that of all the sextants we've looked at, the vast majority with two numbers are Brandis sextants with a US Navy number. We're not seeing British, German or Russian sextants with two numbers, so the pattern we see would lead one to conclude that the box found on Gardner / Nikumaroro is a Brandis sextant that was once in the US Navy inventory approximately during WWI.
The fact that we know Noonan carried such an instrument as his "preventer" make it all the more interesting. If you think about it, a flying boat probably spent as much time on the water as in the air, and a nautical sextant may have been more practical during those surface intervals than an aeronautical octant (I'm not an expert here, just thinking out loud). Most stops on the surface they should have known where they were, but what if you had to land in mid ocean, which instrument would be more useful, octant or sextant?
How box #3500 / 1542 got to Nikumaroro is an interesting question, one that has smoking gun potential if we can connect the dots between the US Navy inventory and Fred Noonan. May not be possible, but sure is interesting to investigate. If only we had the USNO archives at our disposal.
I hope this has been helpful in answering your questions.
Best
Andrew