The KT74 beam tetrode was produced after the war and was designed for use in the audio output stage of universal mains receivers that could operate on DC mains and so did not have a mains transformer.
The audio output was given as 2 W when the anode load was 5,000Ω and the cathode resistor was 300Ω.
The Osram identification label.
The top mica and grid cooling fin.
The classic envelope is 38 mm in diameter, and excluding the IO base pins is 87 mm tall.