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