This chrome-plated instrument has a 5" pole arm with a small cylindrical weight at the end. The 7" tracer arm is adjustable and has an L-shaped tracer point, so that the point is offset from the arm.

This German silver instrument has a 6-1/2" arm with tracer point and 6-1/2" pole arm. The arm lengths are fixed. The tracer arm and pole arm are connected by a hinge and form a circle around the white ...