The CV5830 is based on the EL360 is an output pentode introduced by Mullard in October 1958. The applications are: radar scanning, series regulator and pulse modulator. The ratings given are for pentode use. The data-sheet shows that for high voltage regulator and pulse modulator use the peak voltage can reach several kV.
The envelope has Made in Great Britain and no Maker's name. However, the construction looks identical with the Mullard EL360.
The anode insulators are ceramic as high voltages are involved. The copper supports for the control grid have heat radiating fins at the top.
The wide glass tube envelope is 28 mm in diameter, and excluding the base pins is 93 mm tall.
References: Data-sheet. Type CV5830 was first introduced in 1958.