Gunner's sights and levels usually have both a plummet and a vertical sighting device. The plummet indicates elevation against an arc scale when the instrument is set up along the length of a gun barrel; the sight is used when the instrument is set up transversely across the barrel. This example prevents the plummet obscuring the sight by combining the two into a single freely-swinging arm.
Although the instrument is unsigned and has no obvious indication of its origins, the majority of such sights and levels were produced in Germany. Moreover, the divisions of the scale on the sighting arm correspond to Nuremberg inches, and this may indicate the place of manufacture.