The EX610 is a power triode with a thoriated tungsten filament from the mid 1920s. The output at maximum anode voltage is given as 1.6 Watts. Nine Watts of heater power are required to generate this modest output.
The construction employs a glass rod to hold the top of the electrodes and four struts are taken to the clamp around the pinch stem. In the main image can be seen a small bent glass tube passing into the pinch stem below the clamp, this is the anode connection.
The anode face view.
The ERT brand on the dome together with the filament rating and the maximum anode voltage. The first character of the Type has been lost.
The two filament tension springs and the control grid.
The hooks on the tension springs and the top loops of the filament wire.
The UX4 base pins.
Looking into the anode the shape of the filament can be seen.
The balloon envelope is 59 mm in diameter and, excluding the base pins, is 118 mm tall.
Reference: Datasheet. Type EX610 was first introduced in 1925.