The VMP4 is a screened variable &MU; RF amplifier pentode for use in broadcast superhet receivers.
The VMP4 Catkin was introduced in 1933/4. The improved version the VMP4G was introduced in 1935 as a glass enveloped version when the Catkin valves were phased out. The Catkin in 1934 had a screw top cap. The following year the Top Hat top cap had taken over as the connection method of choice.
The Marconi paper label. The external anode is concealed within the outer screen.
The B7 base.
The screw top connector.
The wide metal tube envelope is 37 mm in diameter, and excluding the B7 base pins is 110 mm tall.
References: Datasheet & 1043. Type VMP4 was first introduced in 1934.