Untested.
Unit appears complete with all major components present, including the perforated steel heat shield, copper bus bars, brass adjustment knobs, removable bridge bar, and original wood base with metal carry handle. Terminals marked 500 and + are intact.
No internal testing performed.
This is an early-20th-century Weston Electrical Instrument Co. portable precision shunt designed for use with the Weston Standard Millivoltmeter No. 19753. These high-accuracy shunts allowed standardized measurement of high currents by producing a precise millivolt drop across the copper bus assembly.
This example features:
500-amp rating (as indicated by the “500” terminal marker)
Heavy copper bus bars
Brass calibration and lock knobs
Perforated steel heat-dissipation enclosure
Engraved instruction bar: “REMOVE THIS BAR ONLY WHEN READINGS ARE TO BE TAKEN”
Original hardwood base and metal carry handle
Early Weston brass ID tag with Newark, N.J. marking
These Weston portable shunts were used in physics laboratories, calibration stations, and power measurement facilities, and they rarely appear in complete form.
Circa 1910–1930