According to Taylor (op.cit.) the trademark Thomas Harris & Son flourished between 1806 and 1846. Thomas Harris had worked at London and Bloomsbury since 1767 and the last news of him date from 1837. His son was probably William Harris and it is not sure whether the trademark Harris referred to the same person, given that there were many craftsmen called Harris.
The telescope in question, with achromatic object lens, is two-draw; the object lens tube is made of wood (probably oak) painted red, the eye-piece tube - extendible - is of brass and bears the words T. Harris & Son / Day or Night. The object lens is slightly chipped, the eye-piece is protected by a sliding cover and on the outer tube is mounted a brass ring, with a pin for hooking it onto a mounting or a tripod.
The 1843 inventory describes it together with a similar model made by West: "Hand telescope by the Englishmen Hakkis [sic] and Son, exactly the same as the previous one. A leather case with baldric (today disappeared) allows one or other of the two telescopes to be transported." As regards the "... previous one", the inventory records "Hand-held telescope by the Englishman West, with achromatic object glass and terrestrial eye-piece in outer wooden tube, and extendible tube in metal, with similar fittings."
The mistaken attribution to Hakkis instead of Harris by the compiler of the inventory, Gaetano Ceschi, is due to the fact that the engraving of the signature is partially eroded. Dating has been computed by analogy with a telescope bearing the same signature and which can be found in the National Maritime Museum at Greenwich. Another telescope by the same author, whose description seems identical to ours, is to be found in the National Museum of the History of Science in Leiden (see Engberts, 1970).

E. Engberts (1970), pp. 82, 102, 136.
An Inventory of the Navigation and Astronomy collections in the National Maritime Museum Greenwich (1970-73).
E.G.R. Taylor (1966), p. 365.