The base says VT-139 - for US Government procurement. On the envelope the commercial Type designations of 0D3 and VR-150 are printed.
The design is of a neon discharge tube whose geometry allows for a nominal stabilised voltage of 150 Volts at around 30 mA. The regulation is 150 plus or minus 5.5 Volts over the range 5 to 40 mA through the tube.
Internally pins 3 and 7 are linked. This shorting link is designed to protect the connected equipment from overload, as when the stabiliser is removed the supplied circuit is disconnected.
The paper label incorrectly identifies this voltage stabiliser as a Thyratron.
The construction has a central rod anode surrounded by a cylindrical cathode.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 86 mm tall.
