The 10P14 is an audio output valve, from 1947, designed for single end use in universal mains receivers. The 100 mA heater clearly identifies that it was aimed at equipment that used a few valves, like a radio receiver. we also have the 20P3 that is identical except for a 200 mA heater. The 10P13 is the same valve designed for a small envelope and B8A base.
The Mazda valve was designed after the time when Mazda gave up their own version of the octal base and adopted the International Octal.
The cathode resistor was designed to be 180 Ohm and the anode load to be 3700 Ohms.
There are heat radiating fins at the top connected to the copper supports of the control grid. Additionally there are V shaped heat radiating fins above the pinch. These are connected to the control grid supports with bright metal ribbons. The fins themselves are attached to copper rods that are embedded into the glass of the pinch.
Another view of the lower grid heat sinks.
The top grid heat sinks.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 78 mm tall.
Reference: 1040. Type 10P14 was first introduced in 1947.