The indicator, the coils and the disk on which the scale is drawn are housed in the upper part of the platform and protected by a removable cylindrical chrome-plated brass case which is closed at the top by a piece of frosted glass.
The indicator and the index, which are attached to the same vertical pin, are completely free to rotate.
One of the extremities of the index turns in the upper half and the other in the bottom half of the scale. The two halves are divided into degrees from 0 to 90 in the right and left quadrants, with zero in the middle.
A button with a spring, placed in the centre at the bottom of the platform, allows insertion of the instrument only for the time strictly necessary to verify whether or not equilibrium has been reached.
On the disk on which the scale is etched there is also the name of the builder and the patent number 137.
On the frame of one of the coils there is the value of their resistance which is 416 ohms at 55°F; on the supporting surface of the wooden base there is the date of its final testing, which took place in Italy on 22 November 1877.