The sextant is the development and improvement of the octant, an invention of the English naval officer John Campbell in 1757. The improvement brought about by the sextant is that the octant has a scale of one eighth of a circle, that is 45 degrees and measures angles up to 90 degrees, while the sextant has a scale of one-sixth of a circle, i.e. 60 degrees, and measures angles up to 120 degrees.

The sextant consists of a fixed arc of 60 degrees, i.e. one sixth of the circumference of the circle, which is calibrated in tenths of a degree, a rotating arm and a mirror system. The movable arm carries one of the mirrors and can be rotated about the fixed calibrated arc, giving an image of the celestial body, the angle of which is measured when this image coincides with the horizon line. When the angle of the sun with the horizon is measured, i.e. its height, during the "meridian crossing", i.e. when the sun is at the highest point of its orbit, this angle corrected with simple tables according to the season of the year, gives the observer's latitude. which is observed directly in the latitude determination. This angle is used to determine latitude.

Finding longitude requires precise timing and complex calculations using tables.

To protect the observer's eyes from bright sunlight, the octants and hexants also have removable filters to reduce the brightness of the light.

This sextant was delivered to Edward Spencer Churchill. Churchill was a notable figure in naval history, best known for his contributions as a naval officer and historian.

Edward Spencer Churchill served in the United States Navy, where he rose through the ranks and gained experience in various capacities. His career spanned important periods in naval history, including World War II.

Churchill was dedicated to the study and documentation of naval history. It focused on preserving historical records and contributing to the understanding of naval operations and strategy.

He wrote several works on naval history, providing information on naval conflicts, naval technology and the development of naval warfare. His writings are respected in academic and military circles.

Through his naval service and academic contributions, Churchill played a role in enhancing the understanding of naval history and its importance in wider historical contexts.

Churchill's work has been appreciated for its depth and the way it sheds light on the complexities of naval operations and strategy.