The EA50 is a miniature signal diode. It was designed to be used in demodulation and other signal rectification. Mullard describe the main area of application as signal detection in television equipment. In the late 1940s television was exclusively VHF based.
This exhibit came complete with B3G base and spring top cap.
The B3G base.
Tiny valve with even smaller diode section within.
The valve out of the holder.
The thin glass tube envelope is 11 mm in diameter and, including the B3G base pins, is 47 mm long.
References: Data-sheet & 1040. Type EA50 was first introduced in 1939.