I agree that 1942 seems to be too late for that low a number. I like your theory that it may have been re-calibrated in 1942 after some kind of damage was done to it.
Please allow me a minor quibble on terminology. Calibration usually implies some sort of adjustment being made to bring a unit into an acceptable tolerance or degree of accuracy. That's not what the manufacturer or the Navy was doing with these. They were checking the uncorrectable errors in the sextant to make sure they were within limits. The errors were tabulated and transcribed to a label that then travelled with the sextant. Sort of a pass/fail exam with no grading on the curve that becomes part of your permanent record. Also a distinction without a difference for most people, but we're not most people, now are we? The sextant owner/operator would perform checks and adjustments to remove side, vertical and index error as part of normal usage.
Barring evidence in favor of your definition, I'd rather take the classification at face value, meaning "used in surveying rather than in onboard navigation."
This is a common naval usage of the word "survey". From
wiktionary , the 6th verb definition "To dispose of after determining that something is no longer useful for its intended purpose (military) "Surveyed Old Rope." -William Bligh." Civil engineers ("those who build targets") have their own instruments such as transits, levels, etc.. I'm going to look for some older Navy construction pieces and see if there are any inspection labels, whether they used the same ones we've seen on sextants (many variations noted so far) and what kind of things show up in the "Class" field, if there is one.
All a sextant can do is measure the angle between the observer and two points or a point and a line. I don't think this is a common need in surveying (not the Supply Corps kind) work and if you do, a transit will perform the job while keeping you on the straight and level at the same time.
Without the rules of the game (policies and procedures for sextant inspection in force at the time), we don't know what the inspector was supposed to put where on the form, but an old Brandis failing inspection and being sent out to pasture is one possible explanation that seems to fit the available evidence.
The "No. No" in the "No." field on the certificate is very strange. Since the box appears to be marked with 1415, the number so prominently struck (rather than engraved?) in an unusual position, and since the box has 3339 very clearly on it, why "No. No"? Could this have been pieced together from parts of two sextants?
They were inspecting sextants, not boxes, and we've seen mismatches in several cases already noted. I suppose someone could have done an arm transplant and produced a Frankensextant, then asked the observatory to check it, but I can't come up with a reason why. Actually it sounds like something I'd do, therefore ruling out the rational man. Meanwhile, I'm trying to get better pictures of the arc, but no word yet.
The subject of this thread is, "Where are the Naval Observatory records of sextant numbers?" If we had the records, we wouldn't need to compile any more data like this. We would know whether there is an entry for a Brandis 3500, N.O. 1542. Cheesy
Ah, yes. Now we get down to the brass tacks. I had a conversation late today with someone in a good position to root around the most likely repositories (I'm not in such a position). He's interested and had some ideas, so
maybe some results will be forthcoming. Even if the results start disproving my ideas, that might help steer additional research.
On another front, has anyone ever checked with Bendix (now part of Honeywell)? There may be some archival stuff from the Pioneer and Brandis acquisitions there.