The VCR139A is a small oscilloscope tube that was also used in early WWII radar. The connections operating conditions and size make are the same as the ECR30 from Mullard.
The VCR139A identification is etched into the neck of the tube and is thus permanent.
On the extreme left the X plates can be seen. Next are the Y plates and unlike the ECR30 the plates remain parallel and do not flare. The gun assembly technique also differs markedly from the Mullard approach. Note also the use of glass beads as both supports and insulators.
The B12B base.
The face of the tube is blemish free. The phosphor is green.
The deflection sensitivity for both X and Y plates is 170 / Va mm/V. The second anode requires a voltage of about 135 Volts. Adjustment of the second anode voltage will adjust the focus of the spot size.
As government surplus after WWII these small tubes were used for home built oscilloscopes. The circuit above was published in 1956 and is typical of the designs used to power these small tubes.
The end window envelope envelope is 42 mm in diameter, and excluding the B12B base pins is 178 mm tall. The screen diameter is 69 mm and overall the length is 199 mm.