original and well-maintained dated c. 1907 american antique industrial single commercial building basement power plant switchboard analog voltmeter designed and fabricated by the weston electric instrument company, newark, nj. the antique electrical switchboard measuring instrument is comprised of cast iron with the original copper-plated finish virtually intact. the ornamented faceplate contains an analog display with pointer arrow that moves along a scale in proportion to the voltage of the circuit. a diminutive riveted joint yellow brass plaque contains a multitude of instrument patent dates. the manufacturer markings and foliated scrollwork are lightly embossed around the detachable circular-shaped face plate. the flat bezel or ring contains three screw holes for mounting flush against a painted black slate panel. standard voltmeters are used for measuring electrical potential difference between two points in a given electric circuit. the analog type contains a pointer that moves along a scale in proportion to the voltage of the circuit. the weston electrical instrument corporation was founded in new jersey by edward weston in 1888, the company's innovations included the weston standard cell, the first accurate portable voltmeters and ammeters, the first portable lightmeter, and many other electrical developments. measures 7 3/4 inches in diameter.