Records of certain Government Departments known to have purchased scientific instruments from designated suppliers over long periods are potentially important sources of information on both instruments and their makers. The Office of Ordnance was one such Department. Investigation of its financial and administrative records has shown that the appointment ‘Mathematical Instrument Maker to his Majesty's Office of Ordnance’ brought the holder a substantial trade in instruments for drawing, surveying, and military purposes. Detailed entries in the Bill Books enable not only (...) types, quantities, and prices of instruments supplied to be determined, but also the purposes for which they were required. In many cases the actual users of the instruments are named, with their locations in Great Britain and overseas.The records of the Office of Ordnance are extensive, covering the mid-seventeenth to the mid-nineteenth century in over ten thousand volumes or bundles. This paper provides an introduction to what is available, and examines in particular the period 1748–1772 when George Adams senior was Mathematical Instrument Maker to this Office. It is shown that during this period Adams supplied over 1500 instruments, ranging from drawing pens to theodolites, detailed in 148 bills amounting to a total value of £2425. Some other well-known instrument makers, such as Thomas Wright, Benjamin Cole & Son, and Jesse Ramsden, were also occasional suppliers of instruments in the same period, while from 1765 onwards the records include bills for instruments purchased by the Office of Ordnance for the Royal Observatory from makers such as Dollond and Bird. The total number of instrument makers' bills located and examined in the period searched, including the 148 by Adams, was 166. In addition, though not within the scope of this paper it was observed that the records contain numerous bills by William Deane before, and by Jeremiah Sisson after, the period of Adams' appointment respectively. (shrink)