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.
This exhibit was made by RCA in America and the neck has etched on it the code 1810PI.
The screen diameter is 65 mm.
The base cap with VCR139A and the old RAF stores code of 10E/466 printed on it.
The RCA logo and Made in USA. It can be seen that the connection wires run within the glass rod supports.
The screen is domed, glass in compression, as glass technology could not manufacture flat face-plates that would not implode if under tension back in the 1930s. Even this small CRT has a force of 35 kg of atmospheric pressure acting on the face-plate.
A close-up of the electron gun and deflection plates. The Y plates are parallel and on the right the X plates are flared.
The end window envelope envelope is 41 mm in diameter, and excluding the B12B base pins is 178 mm tall.