Machlett ML-80 Kenotron

Ref. F4

This tube is 26” (65 cm) long and has a six-inch (15 cm) diameter.

Its specifications remain unknown, but it’s assumed to date back probably to the late thirties or early forties of the 20th century.

The tube carries no maker’s name or type number, but a highly similar tube, described as a Machlett ML-80 Kenotron is seen in the picture below, reproduced from page 83 of E.R.N.Grigg’s book “The Trail of the Invisible Light”.