The 5556 or GL-556/PJ8 is an RF power triode with an anode dissipation of 7.5 Watts and full power rating to 6 MHz and reduced ratings up to the top of the HF band at 30 MHz.
The design use is as an RF power amplifier and oscillator and alternatively as a modulator.
This valve dates to 1945 and so it is unusual to have the supports held in a glass rod.
Side view showing the filament tension spring rising from a support fixed into the glass rod.
The stitched anode and above is the top of the control grid and the filament.
The wide glass tube envelope is 38 mm in diameter and, excluding the UX4 base pins, is 91 mm tall.
