Presented is a museum quality, a term we don’t use
lightly, bronze frame, platinum arc, antique sextant with telescope made by the well known maker Spencer,
Browning & Co. of London, Ca 1870. It is in remarkable original condition and has the label of J. Sewill,
Chronometer, watch & Nautical Instrument Maker, 61 South Castle Street, Liverpool and at 30 Cornhill, Royal Exchange,
London. Of the many Spencer Browning & Rust et al antique instruments we have sold, this is one of the very few metal
frame instruments that has all it accessories present. 
The arc measures from
– 5 to plus 125 degrees. Below the platinum scale on the arc is engraved “Spencer Browning & Co. London”.



Spencer Browning Rust worked
in London from 1724 to 1840 when the name was changed to Spencer Browning & Co. after the death of Ebenezer
Rust.  The successor, Spencer Browning had offices at a number of addresses, including Cornhill and Wapping High

Street, London. They were in business until 1870. They had
an early dividing machine and inscribed arcs for others.
Ref: Gloria Clifton, Directory of
British Scientific Instrument Makers 1550-1851
(London, 1995), p. 261.


born c.1813 was a watchmaker and chronometer-maker in Liverpool. It is thought that Joseph Sewill may have retired to
London in 1862. He died in London in 1895. His son John Joshua who died in 1891 carried on the family business. His brother
Frank succeeded John Joshua but the business was out of the family’s hands by 1905, although the firm is still in existence
in Liverpool. Joseph Sewill is listed as working from 30 Cornhill, London 1870-1890 and 61 South Castle Street, Liverpool
1845-1937. They were best known as maker’s of high grade chronometers, but also offered navigation instruments such as sextants
and quadrants.

This beautifully made sextant
has a ribbed brass index arm measures 9 5/8 inches long on the index
arm. The horizon mirror is on an adjustable turntable and can be rotated by an arbor. Note the thumb screw, early form platinum
vernier scale, reading from right to left from 0 to 20 arc minutes, a removable telescope, and two sets of
sun shades, four for the index mirror and three for the horizon mirror. The handle is made from Ebony which with the
other indicators all of which help date the instrument as from the last quarter of 19th Century.

style stair step keystone case interior
INSTRUMENT CONDITION: The sextant appears in its last
used condition having been maintained properly. The index mirror is in much better condition than might be expected with
little loss of silvering. age. The horizon mirror  is in better condition. The arc’s engraving is sharp
and distinct. The index arm clamp and tangent screw are complete. The shade glasses are complete. Everything is in good
working order. The entire instrument shows as complete and in fine condition. The instrument has its original machinery, and
a telescope and sighting tube, plus an adjustment wrench, pick and telescope shade cap.


THE CASE: The “keystone” or “fan” shaped case
is made from Mahogany, and except for a couple of age cracks is in excellent condition. There is a lock, but
they key are missing. A label of J. Sewill, Chronometer, watch & Nautical Instrument Maker, 61 South Castle
Street, Liverpool and at 30 Cornhill, Royal Exchange, London is in good original condition is inside.
          Horizon mirror
          Vernier reads right to left
A highly
desirable and worthwhile example from one of the better known English instrument makers, and sold by one of England’s finest.
Length of frame 9 5/8″
Width of frame at arc   9 1/4″
Index mirror    48 x 30 mm
Horizon mirror 28 x 22 mm
Weight    3 Lbs  In case 4 Lbs
QUALIFICATIONS: We are one of the few company’s still selling navigation
instruments that know anything about them. For purposes of judging whether Joel’s opinion counts, he was the editor
of the chapter on sextants of the 1977 Edition of “Bowditch”, The American Practical Navigator, NAVPUB 9; a member of the
U.S. Naval Academy Navigation Symposium Board, 1975 -1978; the author of a book on marine sextants, Cornell Maritime Press,1975,
and the founding president of Nautech Maritime Corporation which partnered with Tamaya of Japan in the introduction of the
MS 733 Spica, the MS 833, Jupiter, MS 933 Venus sextants and the famous NC-2 navigation computer, in the U.S. market. Joel
is a retired Master Mariner, and held a U.S. Navy “D” Qualification as a Senior Skipper – Oceans.
six years he was a Varsity Offshore Coach at the U.S. Naval Academy.
This fine instrument is 137 years old,
and is complete in  original condition with a near perfect historic label. A superior addition to any

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