The VR150/30 (also VR150) is a gas filled discharge valve that exhibits a near constant voltage across the valve for currents within the range 5mA to 40mA. The regulation is 150 plus or minus 5.5 Volts.
The side view reveals no additional information.
The construction is of a central cold cathode within a cylindrical anode. As usual the mica supports confer structural stability within the envelope.
The wide glass tube envelope is 30 mm in diameter and, excluding the IO base pins, is 69 mm tall.
References: Data-sheet & 1040. Type VR150/30 was first introduced in 1939.