This is a mobile coil milliamperometer with a horizontal horseshoe magnet attached to the case.
The coil, connected to a spiral return spring, can rotate around a vertical pin in the gap between the cylindrical polar extensions of the magnet and a cylindrical, soft-iron nucleus coaxial with the coil.
The case is a block of bakelite having a square cross section (14.5 x 14.5 cm, height 3 cm). The scale and index are protected by a black-lacquered plate raised by about 1 cm above the part in bakelite. It has a wide glass window for reading the scale. The index is set on edge and the scale is polished to avoid parallax errors.
the screw for the zero correction is on the case; the scale has 100 divisions.
The instrument is equipped with two shunts that increase its range from 50 milliamperes to 1 and 5 amperes respectively.