Simple theodolite, maker unknown, made in Italy, 1600-1630.
Simple theodolites were used for measuring angles during land surveys. This theodolite has fixed sights and a movable alidade. Its umbra versa (vertical) and umbra recta (horizontal) scales enable altitudes (vertical angles) and azimuths (horizontal angles) to be measured. It would have been used with a tripod for stability and accuracy.