The UL46 is a fairly uncommon valve because it is essentially a UL41 audio output pentode constructed with improved internal insulation to enable it to function as a video output pentode, or a line or frame output amplifier in TV service.
It was much more usual for 'P' series valves to be used for such purposes. Mullard describe the UL46 as a video output pentode with a maximum anode dissipation of nine Watts.
This valve is a nearly all glass device. It shows the transition from a metal skirt with locating pip to an all glass format. It has the B8A base with the pins equi-spaced around a circle. The UL46 was in fact one of the last B8A types to be introduced. The B8A was to give way to the B7G and B9A formats very quickly. The locating pip is placed on a wider part of the envelope that is 21 mm in diameter.
The glass tube is not perfectly smooth and some distortion of the internal structure occurs.
The locating pip on the skirt and the heat radiators on the copper supports of the control grid.
The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 69 mm tall.
References: Data-sheet & 1040. Type UL46 was first introduced in 1951.