Precision Apparatus Dot & Bar Signal Generator Model E-420 Made in USA - $36 (Bend)

Precision Apparatus Co, Inc White Dot & Bar Signal Generator, Model E-420.
It was made in Glendale, New York.
A dot & bar generator produces a known good video signal with test patterns for adjusting the screen alignment of televisions.
Common patterns include a series of dots and vertical and/or horizontal lines that aid in adjusting the display.
They also produce a series of bars that allow checking the correct display of shades of gray.