The A2134 pentode is clearly designated as an audio power valve. In class AB1 a pair of valves in push pull will deliver 13.3 Watts. The input needs 30 Volts peak to peak and the anode load has to 7500 Ohms.
Also the data-sheet specifically mentions suitability as a series pass valve in stabilised power supplies.
In Class A, triode connected, the valve will generate 2.6W at 1.4% distortion.
The anode end view.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 62 mm tall.
References: Data-sheet & 1040.