Tektronix 1420 en Webster, Massachusetts, USA

This Vectorscope is a compact television equipment testing device designed to display and measure chrominance information from a composite color video signal.
The chrominance information, saturation, and hue are displayed on the CRT in a polar plot fashion.
The radius of the polar plot is a function of saturation and the peak to peak amplitude of the chrominance signal.
The angular (phase) displacement is relative to the hue information, phase difference between the chrominance information and the reference vector (burst).
A or B channel selection is possible with the front-panel switch.