The W143 is a variable μ amplifier pentode. It is equivalent to the Mullard EF22.
The B8B base with equi-spaced pins and a central locating spigot.
The coating on the inside of the glass, probably to reduce the release of gas from the glass, obscures the inner structure. The mesh screen and the cathode tube can be seen.
A closer view of the top mica.
The wide glass tube envelope is 27 mm in diameter, and excluding the B8B base pins is 62 mm tall.