The Gammatron HK54 from Heintz & Kaufman dates from the late 1930's and was designed for use as a VHF transmitter Power amplifier. The tantalum anode has a 50 Watt dissipation and the maximum anode voltage is 3,000 V. The anode will glow cherry red at full dissipation.
The datasheet also gives ratings for use as an audio frequency modulator operating in Class B push pull. The base is ceramic for low RF loss in damp or airborne applications.
The etched lettering is particularly clear showing the HK logo. The HK24 exhibits we have show faint lettering.
The tantalum anode with side fins for greater radiating area. The connections have glass beads where they pass through the envelope. The squirrel cage grid can be seen.
The grid connection.
The Gammatron trade name and the anode and anode connection. Note the red plat where the connection passes through the glass. This simple looking anode support is made of four pieces. Three vertical and one strap.
The grid and helical thoriated tungsten filament.
In this image the filament is easily seen and with care the wire ring holding the grid wires in place can also be determined.
The wide glass tube envelope is 51 mm in diameter, and excluding the UX4 base pins is 125 mm tall.
References: Datasheet. Type HK54 was first introduced in 1938.