The X22 is a battery heptode or pentagrid mixer for use in broadcast receivers including short wave bands. The valves were metalised for shielding but this exhibit has shed the zinc paint revealing the electrode structure and the original etched lettering. X22 has the metal paint in place.
The pin connections presented come from Thrower as the reference in Radio Valve Data appears to be incorrect.
The pad holding the wire that originally connected the metal loaded paint to base pin six.
A close-up of the bright anode with wire grids within. The filament tension spring is held on a mica sheet above the top mica that holds the electrodes. Signal injection is via g4 that connects to the top cap.
The top mica. The screen grids g3 and g5 are close wound and enclose the signal grid.
The lower mica and pinch.
The classic envelope is 44 mm in diameter, and excluding the B7 base pins is 107 mm tall.
References: Datasheet, 1040 & 1043. Type X22 was first introduced in 1937.