The Ameliapedia page on the Sextant Box has a Chart listing U.S. Naval Observatory Numbers, manufacturer numbers and Eccentricity Certificate dates for a number of sextants that have turned up in museums, ebay, etc. Following the chart is a discussion by Ric and Art Rypinski about (perhaps I’m simplifying) what those numbers might imply about when a sextant with Gallagher’s numbers (3500/1542) might have last passed through the Naval Observatory.
Art, citing the Smithsonian, says that that the manufacture of Brandis instruments ceased in 1932 and goes onto say that “ …it would be reasonable to believe that almost all of the Brandis sextants in circulation were actually manufactured in 1918-1920, and that none were manufactured after 1932. Further, the Naval Observatory appears to have changed its numbering plan (at least for aviation octants) in the late 1920s, and begin issuing NO numbers with the form XXXX-YY, where YY was the year of original calibration. Therefore, I believe that all of the post-1930 calibration dates are recalibrations of sextants that were originally calibrated and issued their NO numbers in 1918-1920…”
Looking at the numbers in the chart, I couldn’t follow why Art thinks the Naval Observatory changed its numbering plan in the late 20s to use a six digit i.d. code: the only sextants I see on the chart with six digit ids have certificates dating from the 40s. But I do think the numbers in the chart suggests that Art is right about most sextants having been manufactured in right around WWI and that some of these sextants were later given new eccentricity certificates.
I don’t have a deep statistical analysis to present, but I do think it is interesting to forget about the manufacturer’s numbers and look at the frequency of distribution of Naval Observatory numbers and certificate dates as shown below:
# of
N.O # Sextants Date Range (# of certs)
0 to 999 7 1918 to '43 (3)
1000 to 1999 17 1918 to '42 {8)
2000 to 2999 9 1919 to '46 (6)
3000 to 3999 0 N/A
4000 to 4999 14 1938 to '44 (3)
5000 to 5999 5 1945 to 1945 (2)
g.t. 6000 2 1946 (1)
The second column of numbers shows how many of the 54 sextants in the Ameliapedia chart fall into each of the seven Naval Observatory number ranges. The third column then gives the range of certificate dates for the sextants in each range, and the numbers in parentheses gives the number of certificates in each range. Have I lost anybody yet ?...
A couple of things are interesting when the numbers are viewed this way:
-We see certificates ranging from 1918 to the mid-40’s for sextants in the first three ranges of Naval Observatory numbers, i.e. numbers less than 3000; A simple explanation is that sextants having these N.O. numbers were produced around WWI, and some of them remained in service in the Navy and received new eccentricity certificates many years later. This is consistent with Art’s remarks about re-certification of sextants the Ameliapedia discussion.
-We don’t see any WWI vintage certificates in the last three N.O. number ranges, i.e. those greater than 4000; A simple explanation is that the USN didn’t start assigning sextants with numbers greater than 4000 until WWII was looming. Note however that back on the main Ameliapedia chart many Brandis sextants have N.O. numbers in the 4000-4900 range. Art tells us that Brandis stopped making sextants in 1932, and Art (I think correctly) believes that most of the Brandis sextants are of WWI vintage (the Navy had a glut of sextants after WWI, so it doesn’t seem likely they would have been buying more Brandis sextants from 1919 to 1932 the year of Brandis’s demise).
Maybe the Navy stockpiled unused WWI-vintage sextants that never got N.O. numbers assigned to them and pulled ‘em out of storage for use in WWII? I don’t like that explanation much, but it would explain things…
- We don’t see any sextants with N. O. numbers in the 3000 range. Assuming this isn’t a statistical fluke, the only simple explanation for the gap in numbering that I can think of is that for some reason no sextants were ever given N.O. numbers in the 3000-3999 range. Maybe the Naval Observatory misplaced its master list of sextant numbers after WWI, and when WWII started to loom some old fart in the eccentricity shop remembered they left off numbering sextants somewhere in the high 2000s? Another not so great explanation…
If this post is total nonsense, please forgive me—it’s 3 AM and maybe I’m not thinking straight…
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note added: I hope to get another post up soon about the sextant numbers which I think may make the absence of and 3000-series sextants seem even a bit odder than it seems now...