It is isn't what I don't know that gets me in trouble, it is the things I do know that aren't true. My recollection was that the NO number was generally placed on the sextant arc, and the maker's number elsewhere.
I agree that the NO number is generally placed on the sextant arc. I've got a couple of photos of nice numbers on arcs in the photo gallery
In this case, the "5317" is on the Certificate of Inspection--but there is no inscription for the NO number on the slip--that line was left empty:
If the number is in the middle of the arc, and hand etched, it is probably an NO number.
Agreed. The seller describes the hand-etched NO number with the stylized "NO" symbol. Though the seller does not provide a picture, I think the claim is reliable. Here is an example from 3987/1584:
If it is at the end of the arc and die stamped, it is probably a maker's number. So the number at the end of the arc and printed on the case is likely the maker's number, "4193," just as you say.
Agreed. Here is 3987:
That leaves open the question of the reference to the maker's number of USNO ticket, 5307. We can see it isn't 5307. Is the ticket for a different sextant, or did the USNO guy put the USNO number in the wrong place on the form? Then there is the seller's reference to "4161" as the USNO number, but no photo. Is 4161 the "real" USNO number, and 5307 just a red herring?
If I had to bet, I would bet against 5307 being the real maker's
number, though I cannot come up with a plausible fairy tale to account for how the wrong number wormed its way into the box for 4193. A correction slip for the wrong sextant must be worse than useless, I would think.
The anomaly doesn't destroy the observation that there were a lot of Brandis sextants that had two numbers assocated with them. The Niku box, 3500/1452, is still in the running. This box does not have the NO number on it, as some other boxes do, but I don't see what conclusion, if any, could be drawn from that oddity.
Life is like that!