This is a superb example of a Box/Pocket Sextant, as would have been carried by an officer/gentleman, in order to determine his exact position in the field . A compass would also be carried to determine direction.

Manufactured in brass, and now to a very fine oxidised green finish,  almost "as new",with only very minor traces of scuffs and superficial fine scratches.

Complete with adjustable mirrors, silvered venier scale, adjustable arm, turnscrew, extendable 2 pull brass telescope,  retractable sun filters, and a hinged arm with magnifying glass.
Signed on the periphery of the working surface;

"Troughton & Sims London".

Also, embossed to the top exterior surface in gold lettering;

"C.F.A.C"

There is a superb leather case, of the highest quality, complete with a hinged lid, closing tabs, all with sound, intact stitching, and finished to the interior with a Burgandy red lining.
The same initials are clearly stamped to the side of the exterior.  The leather is to a fine patina of age.

Documented research reveals that this instrument belonged to 
Cecil Francis Adrian Cooper, born Sept. 1876.    After training on
HMS Worcester, he enlisted as a private in the Oxfordshire Yeomanry in 1900, Regimental number 7954, 40th Co. Oxfordshire Yeomanry 10th battalion.....  redesignated as Imperial Yeomanry in Dec.1899.
He arrived in South Africa for the Boer War in Febuary 1900, where the 3rd and 10th batallions fought Boer volunteers.
Later, he served in World War 1, in France from 1915, as a Lieutenant with the Army Service Corps, and then as T/Captain in the Royal Service Army Corps.  He returned home in June 1920, and later died in 1939, aged 63.

A rare item, both as an example of a highly collectable instrument, by an an important maker of such fine instruments, and, an interesting piece of military history.