Henry Glover, New York label

Presented is an ebony frame, ivory arc, antique sextant
made by the quality maker Spencer Barrett & Co. of London. It is Ca 1850 – 1870. The instrument is in sound
condition with well made metal machinery, and Spencer Barrett’s signature sharply engraved ivory. It is housed in
a keystone case which is in good condition considering its age.
The arc measures
from – 3 to plus 105 degrees. The ivory plate on a cross bar between the two limbs is engraved “Spencer Barrett & Co.
The label is that of Henry Glover who was active in New York as
a chronometer and instrument maker in many locations there until 1872. He is listed in Webster’s database of instrument makers. 
It was priced at $18.00.

There are many examples of Spencer Barrett instruments in museums, and they are listed
in Webster’s Database of Instrument Makers, but little is known of their history other than they were active between about
1830 – 1880. A similar example of this instrument in the Smithsonian Museum. See
Spencer Barrett was in business in London from about 1830 to 1880, specializing in instruments for navigational use. There
is no connection between them and the more prolific Spencer Browning & Rust Co. which ceased business in 1870.
This well made instrument has a ribbed brass index arm measuring over 12 3/4″
long with a diameter of arc of 10 1/2″. The horizon mirror is on an adjustable turntable. There are three rectangular
sun shades and a single circular horizon shade. This sets this instrument apart from others which were only fitted sun shades.
Note the early form ivory vernier scale, reading from right to left from 0 to 20 arc seconds, two hole peep sight with
“flap”, and three sun shades all of which date the instrument. Its larger size and lack of  a handle on this instrument mark
it 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 this

INSTRUMENT CONDITION: The index mirror is degraded
around the edge, but has a good center reflective surface. The horizon mirror is in good condition. All the ivory
is in perfect condition,
and the engraving is sharp and distinct. Missing is a small ivory pencil
which is typical and may never have been present. The index arm clamp, and shade glasses are complete and in good working
order. One spring clip on the tangent clamp is broken off. This is insignificant. The ebony frame is without cracks. The instrument
has its original machinery, and a two hole peep sight. Everything is original and in good working order. There is green verdigris
over much of the brass indicating its years at sea.

THE CASE & LABEL: The “keystone” solid Mahogany
case is in good solid condition. It is very clean inside with a small hole, and the lower right hand corner has
been replaced. There is a lock, but no key. The label is that of Henry Glover who was active in New York
as a chronometer and instrument maker in many locations there until 1872. He is listed in Webster’s database of instrument
Maker’s Name
Vernier scale
              Peep sight and horizon
Machinery and index mirror

All in all,
a highly desirable and worthwhile example from one of the higher quality English instrument makers
Length of frame 12 3/4″
Width of frame at arc 10 1/2″
Index mirror 45 x 30 mm
Horizon mirror 24 x 20 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.

For six years he was a Varsity Offshore Sailing Team Coach at the U.S. Naval Academy.
Some of his memberships include the: Association of Naval Aviation, Silver Wings,
The Tailhook Association, Naval Academy Sailing Squadron, McCampbell’s Aces Squadron, Naval Historical Foundation, and
the Naval Order of the United States. 

Rarely do you find an instrument that is that
is 166 years old in this original condition with a perfect case. A superior
addition to any collection

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