The 8AL9 is a Compactron triode pentode, although the main picture shows that it is constructed as a beam tetrode. The valve is designed for 600 mA series heater chains in American 525 line television sets.
The frame grid pentode has a gm of 30 and this is required for effective service as a wideband video amplifier.
The triode is a general purpose type.
The triode face view. The control grid is wound on copper supports.
With the small triode seen end on the pentode is face on to the camera. The bright sheet is the electrostatic screen. The screen grid is wound on copper supports.
The dome carries the identification etched in place.
The wide glass tube envelope is 29 mm in diameter, and excluding the B12C base pins is 53 mm tall.
Reference: Data-sheet. Type 8AL9 was first introduced in 1970.