$1000 USD + postage

A fine eight inch radius double frame sextant in flame mahogany case c.1865


13 x 11 x 5



Country of manufacture

UK and Ireland

Categories: Navigational instruments, Calculating, Surveying Instruments & Mining, Engineering antiques, Other Technology Antiques, Tools


A fine 8 inch radius combination brass, anodized brass and black enamel DOUBLE frame sextant by John Crichton of London c.1865. Serial number is quite late (2730) and is this year the company became Crichton & Son. Also, the trade label in the lid of the box is for C.R. Sherman & Co. of New Bedford, MA. (USA) and he commenced his business in 1865.

The sextant is untouched (retains about 50% original lacquer to the front surface, more to the rear). It has an eleven (11) inch arc circle running out to 140 degrees with silver scale (again untouched). The silvered vernier is of typical form and function (worm and screw with locking tab) reading out 20 degrees in 1 minute intervals. It can be read by small flip down mirror directly or by swinging arm magnifier. The main index mirror is 95%, the secondary split mirror is very good as well. There are 7 coloured filters, fore and aft of the secondary mirror ( 3 round – anodized and 4 brass square-all intact). The frame is true and straight. The shaped, ebony handle has an old (stable) 1 mm. shrinkage crack running through the center. There are 2 frame retaining screws missing on the back side (my guess is somebody  hung it on a wall, top and bottom, using the last two holes for string or wire and then never replaced them) !! The sextant comes complete with three (3) eyepieces, 2 with solar filters, one with a clear sighting optional cover. The longest (high power) tube has  internal square grid lines ( 9 quadrants), the smaller tube has a 2 line grid work and the smallest has a singular lens system. All are in untouched, unpolished condition with NO defects. 

The flame mahogany case retains it’s original green baize liners with trade label and measures 13 x 11 1/2 x 5 inches deep. It is missing one hook, the key for the intact lock and a corner on the back. The top has magnificent wood figuring. The bottom has a crack. There are no other issues with the case construction as you can see from the side view dovetailing.

Crichton is using bright brass for the frame here, with anodized brass for the round colour filters and japanning ( 3 chips to the paint) for the base of the primary mirror. With this combination of materials, I am dating this instrument to about 1865. 

Charles R. Sherman of New Bedford, Massachusetts was initially an importer of instruments in 1865, then went on to make his own instruments with his partners (Sherman & Co.) and was the author of navigational texts, as well. c.1870.

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CA ScientificaOpticae

Scientifica Opticae

Mark Hacking (Scientifica Opticae Inc.) has been an avid collector/dealer for over 30 years. A former Science teacher, he has an innate love for anything natural or mechanical. Specializing in optical (microscopes, telescopes), surveying, medical, weighing and drawing instruments, he is an active participant of the Scientific Instrument Fair in London. Living in Stratford, Ontario, Canada, with his wife and two children; Mark looks forward to meeting as many fellow collectors as possible, and has a worldwide following on eBay (Sciopti).

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