Theodolite is a basic surveying instrument of unknown origin but going back to the 16th-century created by the  English mathematician Leonard Digges; it is used to measure horizontal and vertical angles.This  model, called octagonal, is the most frequently encountered. Once disassembled, the foot is retracted and screwed inside the body of the instrument. Everything  fits  in a small and robust box.
Mid 19th to early 20th . Complete with the thin wire present