The 1V (or 1-V) is an indirectly heated half wave rectifier. This exhibit by Champion was licensed by RCA.
RCA, in 1940, describe the 1-V as being mainly for renewal purposes in AC/DC and automotive receivers.
Here the construction can be seen, the top mica is an interference fit to the top of the envelope and prevents internal vibration.
Although reflections from the glass spoil the image the construction can be seen. The central working cavity is small in relation to the area of anode surface used for heat radiation. A process enhanced by the blackening of the metal.
The classic envelope is 38 mm in diameter, and excluding the UX4 base pins is 89 mm tall.
References: Data-sheet, 4055 & 1043. Type 1V was first introduced in 1939.