This exhibit is a radiation detector. The label gives the operating voltage as 410 Volts.
Thanks to Rob Coleman for the identification. The G10H is almost identical but has a working voltage of 400 Volts.
The construction is of a thin outer cylinder with a central metal rod within.
The top of the envelope. The central rod is fixed into a glass support suggesting a high operating voltage.
The wide glass tube envelope is 27 mm in diameter, and excluding the B4 base pins is 185 mm tall.
References: Observation and Rob Coleman.
Absolute Maximum Operating Conditions¶
Updated April 27, 2019.