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 P220A has double the output power.
The dome of the envelope carries the identification etched into the glass.
The balloon envelope is 45 mm in diameter, and excluding the B4 base pins is 93 mm tall.
References: Datasheet & 1043. Type P220 was first introduced in 1929.