The base says VT-139 - for US Government procurement plus the commercial Type designations of 0D3 and VR-150. The commercial designations are etched into the glass.
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 etched Type designations.
Unlike UK Government CV valves that do not carry the maker's name the American valves do, here it is RCA.
The cylindrical cathode with central rod anode.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 91 mm tall.
