5 in reversing plane theodolite reading to 1 minute of arc. 4-screw levelling head.
Used for measuring horizontal and vertical angles in land surveying and for setting out works.
For the tripod see https://ice-museum-scotland.hw.ac.uk/product/1977/016-1/.
A book of instructions for the use of theodolites is in the collection (see https://ice-museum-scotland.hw.ac.uk/product/1998-001/).