The P220 triode from Mazda is a low wattage audio output valve for battery radio receivers. The load impedance is 10,000 Ohms and the power output is given as 180 mW.
The dome of the envelope carries the identification etched into the glass.
The getter carrier is attached to the side of the anode. The anode is bright with ridges pressed into the thin sheet to give dimensional stability. The filament tension springs sit on a second mica sheet. Neither of the micas fit tight to the glass.
With a single grid the anode is much wider than the front to back dimension.
The classic envelope is 39 mm in diameter, and excluding the B4 base pins is 92 mm tall.
References: Datasheet & 1043. Type P220 was first introduced in 1929.