The PM2B is a double triode audio output valve from 1933. Like similar valves this was designed to offer reasonable volume at minimum consumption from dry cell HT batteries.
The input voltage is quoted as 40 Volts peak to peak into a 4,000 Ohm impedance. The anode load is given as 14,000 Ohms, and the operating class as B2.
To drive the PM2B more power was required than could be supplied from the PM1HL and a suitable valve for use as driver was the PM2DX.
The classic envelope is 38 mm in diameter, and excluding the B7 base pins, is 95 mm tall.
References: Data-sheet & 1043. Type PM2B was first introduced in 1933.