The Y63 is a second generation tuning indicator with a 6.3 Volt heater. This type of indicator was used in many radios. This exhibit carries identification information in a typical M-OV style. The data-sheet gives that the 6G5 is electrically identical to the Y63 but has a UX6 base cap.
The paper label brands this M-OV product to the Marconi range.
Unlike the Y63 in the HMS Collingwood collection this exhibit enables the electrodes to be observed. The triode amplifier with its copper grid supports sits below the display bowl. The cathode tube is un-coated between the two valve elements.
The display with the cathode coated within the capture area of the bowl.
The classic envelope is 36 mm in diameter and, excluding the IO base pins, is 87 mm tall.
References: Data-sheet & 1040. Type Y63 was first introduced in 1937.