Tangent Galvanometer
Information about this Object.
This is a Chicago Laboratory Supply & Scal Co. Tangent Galvanometer. A current through the wire loop will deflect the compass needle so the effect of the magnetic field may be measured. There is a lift lever on the side of the apparatus to raise a brass locking bar for the compass needle.
Another example with more explanation of a tangent galvanometer at the UQ Physics Museum.
Also see the Wikipedia page on Galvanometers; there are tangent galvanometers near the bottom of that page.
Download the USDZ AR file for this object
Photograph of front of object: