W. C. Cox Theodolite
"Mathematical Practitioners of Hanoverian England 1714 - 1840" by E G R Taylor lists the following entries for William Cox.

Entry 1108  in the 1800-1809 Section - Cox, William, Mathematical instrument maker ( fl 1806 ) ; Plymouth Dock, Devon.

Entry 1517 in the 1820-1829 Section - Cox, William Charles, Optical and Philosophical Instrument Maker ( fl 1820 ) Fore Street, Devonport.

There were no entries for Cox in the 1810 - 1819 section which I believe to be an omission as Devonport and Plymouth Dock were basically the same place.

This theodolite is very early 19th century, although it looks to be manufactured in the late 1700s with the slide mechanism for focusing of the telescope, even though the signature tells of a date 1810- 1820.

The instrument retains most of the original gold lacquer finish with an inverted half circle with parallel telescope signed on the silvered compass dial " W. C. Cox Devonport".

The outer 360 deg circle is divided in single degrees reading by vernier to 3 minutes of arc.

The silvered compass dial has four 90 degree quadrants divided into degrees.

The vertical arc has two 90 degree quadrants reading to 3 minutes of arc.

The telescope is 12 3/4 inches long and the compass is 3 3/4 inches diameter.

The instrument is complete with lens cap and tool with locating pin to fix the position of the telescope in the level position.

The theodolite, at 200 years old, is the oldest in my collection.