The HY615 is a power triode for oscillator and class C amplifier use. The valve looks as if it is intended to work into the VHF region.
In oscillator and amplifier use the driving power is given as 0.4 Watts and the output power is quoted as 4 Watts. For class C amplitude modulated use the driving power rises to 0.8 Watt and the output power is 5.5 Watts.
The IO base is ceramic.
From the side the retaining micas can be seen. The electrode assembly lies horizontally to give minimum distance to both top caps. The anode goes to one and the grid to the other.
The electrode assembly is 11 mm wide, 16 mm long and 4 mm thick. Such dimensions would easily fit into a B9A style envelope, and show the process of miniaturisation at work.
The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 47 mm tall.