Electrical Resistance Tester Appraisal

Antique Wheatstone Bridge / Resistance Box

The item is an antique or vintage electrical measuring instrument, likely a Wheatstone bridge or a precision resistance box, housed within a wooden case. The case appears to be made of a dark-stained wood, possibly mahogany or walnut, and shows signs of age with a discernible patina. The interior of the lid, partially visible, is lined with red felt or velvet, with some elements indicating potential compartments for accessories. The primary functional components are mounted on a dark, possibly ebonite or bakelite, panel. These components are predominantly brass or bronze, showing oxidation and some tarnishing consistent with age and use. Notable features include numerous brass screw terminals or posts arranged in rows, likely for making electrical connections. There are also several switch-like mechanisms, possibly plugs or key-operated switches, with black or dark brown insulating handles. A prominent circular dial with a brass bezel and a white or cream-colored face is visible, likely an analog meter or galvanometer, essential for null detection in resistance measurements. There are also several horizontal brass strips, which might be busbars or sections of the resistance network. The overall construction appears robust and indicative of precision engineering for its period. The visible wear, such as surface scratches on the wood and tarnishing on the metal, suggests a history of handling and display. One textual marking is partially visible on a vertical strip, possibly reading 'Laboratory' or a similar designation, which could indicate its intended use or manufacturer. The estimated age is late 19th to early 20th century, given the materials, construction style, and the appearance of the electrical components.