Maker: Cutler-Hammer Mfg. Co., Milwaukee, Wisconsin
Patent: January 7, 1890 (as stamped on the brass plate)
Item Type: This is a motor starting rheostat / controller, designed for DC motors (110–125 volts), limited to 1 horsepower.
Markings: Terminals are clearly labeled LINE, ARM (armature), and SHUNT FIELD – classic configuration for early DC shunt motor starters.
Use: These were used to gradually bring a DC motor up to speed by inserting resistance in series with the armature, then reducing it as the motor accelerated. The coil visible on the right is the starting resistor element.
Historical Note: Cutler-Hammer was founded in 1893 by Harry Cutler and Edward Hammer in Milwaukee. They were among the pioneers of industrial electrical control equipment. This unit represents an early example of their core product line – motor starters and control gear.
The 1890 patent and the style (slate panel, brass fittings, wooden base) suggest manufacture between 1895 and 1915.
By the 1920s, designs typically had more enclosed housings and cast-iron cases; this open-faced style is distinctly earlier.