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On Sep 29, 2019, at 13:16, Geoffrey Kolbe <NoReply_GeoffreyKolbe@fer3.com> wrote:

I have a Husun sextant, No. 39377, which I date to about 16  Feb 1944 (There was no certificate with the sextant when I bought it). The sextant had obviously had a long life in a salt-laden environment and was heavily oxidised when I bought it about 35 years ago. I have undertaken a restoration on the sextant, still ongoing, which has included stripping and repainting it, making a new mahogany box for it and replacing the index and horizon mirrors. I opted for front coated mirrors (with quartz over-coating to protect the aluminium) to replace the rear coated mirrors. The small optical company who did the job wanted to make new mirrors using new glass to ensure good adhesion of the aluminium on the glass. When an expert offers advise, I tend to take it.

I have yet to test the accuracy of the arc on this sextant, but my suspicion is that in keeping with other Husun sextants of this period, it is not that accurate. Of course, the oxidation of the tangent screw and the rack on the arc does not help in this regard. 

Geoffrey Kolbe