The EF54 is a VHF high-slope pentode and has a sharp cut-off. The cathode is brought out to several pins to provide a low inductance path, part way to a ring connection as found in co-axial valves. A feature of the EF54 is aligned grids that provide conditions to reduce partition noise.
The EF54 was developed from the EF50 and was capable of operation up to 200 MHz.
The all glass construction is covered with an aluminium screening can in the same fashion as the EF50 et al with a metal base cover that houses the evacuation tube within the locating spigot.
The wide glass tube envelope is 33 mm in diameter and, excluding the B9G base pins, is 59 mm tall.
References: Data-sheet & 1043. Type EF54 was first introduced in 1947. See also 1947 adverts.