Vintage USA MADE KNIGHT Voltage Calibrator Electronic/Radio Test RCA 12AX7 TUBE

From the estate of my Dad's best friend Gabe who was a Western Electric Test Set Technician and ham radio operator

Designed to be used with old service grade scopes that did not have calibrated voltage scales. You set up a waveform display between two graticule lines on the scope and then switch this in, match the level and read the P-P value of your waveform from the dial settings. It produces a nearly square wave trace but assume it needs to be calibrated and the one electrolytic replaced. It contains a 12AX7 and an 0A2 tube

No returns, please

Thank you