The EF50 was the ubiquitous red valve for a decade but this unbranded example has a different red paint to that normally seen and that makes it worth including.
The EF50 was designed in 1938 by Philips of Eindhoven for Band I television receiver use and first released in 1939, this amplifier pentode was a general workhorse. It was extensively used in radio and radar during WWII. One additional reason that so many existed was that they had a short life and so were changed often.
They are an early all glass design with an outer aluminium screen can that also served to hold the base and spigot in place. The pins are equi-spaced around the circumference of the pin circle.
The reverse of the screening can is plain paint.
The wide glass tube envelope is 34 mm in diameter and, excluding the B9G base pins, is 60 mm tall.
References: Datasheet & 1040. Type EF50 was first introduced in 1939.