I artiklen Evolution of the Sextant (af A. N. Stimson, Head of Navigation Section, Department of Astronomy and Navigation, National Maritime Museum, Greenwich, England) findes en liste over karakteristika, der kan være med til at tidsbestemme oktanter (se artiklen på: http://home.earthlink.net/~nbrass1/cardart.htm). På listen nedenfor er de karakteristika, der findes på akademiets oktant understreget.
Characteristics Used in Dating an Octant
Dated instrument
Maker's name on
instrument or box label
Owner's name on instrument or box
Presence of backsight
Wooden index arm vs. brass
Flat brass index arm vs. braced
Absence of locking screw on index arm
Locking screw vs. locking screw and tangent screw combination
Presence of vernier scale
Type of vernier scale division("10 - 0 - 10" vs. "20 - 0 -
20")
Presence of vernier magnifier affixed to index arm
Type of wood used in frame construction vs. brass
Size of instrument
Evidence of ivory construction of some components
Presence of wooden "feet" vs. turned brass
Presence of optics vs. peep sights
Presence of handle
Configuration of box (stepped keystone vs. keystone vs. rectangular)
Construction of box (type of dovetailing if any)
Configuration of filters (shades)
Information found on paper gasket inside pivot point