This theodolite was probably made in the third quarter of the 18th century, its basic form deriving from the design that Thomas Heath had introduced as early as 1725.
A trade catalogue published in 1765 titled Mathematical, Philosophical, and Optical Instruments Made and Sold by Heath and Wing, describes similar instruments under the title ‘Theodolites of the latest Improvements by T Heath’.
Heath trained several notable apprentices, his last protégé being Tycho Wing, whom he took into partnership in 1753. The business was based near Exeter-Exchange in the Strand, London.