Presented is a museum quality, a term we don’t use lightly, ebony frame, ivory arc, antique sextant with
peep sight made by the well known maker Spencer, Browning & Co. of London, Ca 1860. It is in remarkable original
condition and has the label of Samuel Thaxter & Son, No. 125, State St., Boston which is also in excellent original
condition. Of the many antique instruments we have sold, this is the first instrument that we have offered that includes
the small ivory plate on the back, and an ivory cap to hold a lead pencil which is in place. 
The arc measures from – 5 to plus 105 degrees. The ivory plate on a
cross bar between the two limbs is engraved “Spencer Browning & Co. London”, Additionally, in the center of the ivory
degree’s scale between 50 and 55 degrees is inscribed in script “SBR” identifying the ivory was engraved by Spencer,
Browning & Rust, of 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 on Wapping High
Street, London and 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.


is of Samuel Thaxter who was born in Hingham, Massachusetts in 1769 and died 1842. He apprenticed to William Williams, maker
of a backstaff in 1768 with a King Street, Boston address. Upon Williams’ death in 1792 Thaxter took over the nautical instrument
making business, moving to Long Wharf, State Street, Boston in 1792. His address was first advertised as “Head of Long Wharf”.
During the 18th century, prior to the advent of street numbers, a business location was quite often identified by a landmark,
such as “At the sign of the Little Admiral” or “Head of Long Wharf.” From Webster’s Registry of Instrument Makers,
(1792); 125 State Street (1796-1842); both in Boston, Mass.”
He is first listed in the 1796 Boston
Directory as a mathematical instrument maker.  In the 1822-23 edition, the business is listed as Samuel Thaxter &
Son (Joseph H. 1801-1835).  Samuel Thaxter’s grandson, Samuel Thaxter Cushing (1821-1882), took over the business around
1843. Upon the death of Samuel Thaxter Cushing, his widow, Abby C. Cushing took over management of the business until 1905
at which time Herbert Risteen Starratt became manager.  The last entry of the company (Samuel Thaxter & Son) in the
Boston Directory is 1916.”

Reference:  Smart, Charles E.   The Makers
Of Surveying Instruments In America Since 1700
  Troy, New York:  Regal Art Press.  1962

This beautifully made sextant
has a ribbed brass index arm measures 11 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
ivory vernier scale, reading from right to left from 0 to 20 arc minutes, a movable peep sight, and a set of
three sun shades. There is no provision for a handle on this sextant which with the other indicators all
of which help date the instrument as a transitional piece between an octant and a sextant.

Some time after 1780, the addition of a tangent screw, as fitted
to this instrument, allowed for fine adjustment and represents one of the two major changes in the basic operation of
the octants and sextants for the next 150 years! The second was the fitting of telescopes. As was the practice with octant’s
of larger size, this sextant was not fitted with a handle which indicates it is one of the earliest of that type made by Spencer
Browning making it a noteworthy instrument by this maker.

Early 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 has lost its silvering, but is in otherwise good condition. The ivory
is in perfect condition, except for some age darkening at the ends. The 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 and ebony frame shows as near new. The instrument has its original machinery, and a two hole peep sight.

THE CASE: The stepped “keystone” solid Oak case
is in excellent condition, but has some age cracks top. It has been refinished. There is a lock, but
a cover plate and key are missing. A label of Samuel Thaxter & Son, No. 125, State St., Boston which is
also in excellent original condition is inside.
 Maker’s name
“SBR” imprint at 55 degrees
The machinery
A highly
desirable and worthwhile example from one of the better known English instrument makers, and sold by one of America’s finest.
Length of frame 11 5/8″
Width of frame at arc   9 1/2″
Index mirror    47 x 30 mm
Horizon mirror 28 x 22 mm
Weight    2 Lbs 2 oz
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.
Rarely do you find an instrument that
is that is 167 years old in this original condition with a perfect historic label. A superior addition to any collection.