The GR27-56 is a miniature voltage stabiliser designed to stabilise a current of around 0.3 to 6 mA. The striking voltage is 140 Volts and the maintained voltage varies from 70 to 90 Volts depending on current.
The glass pinch with the two electrodes. The lower electrode is a flat plate and the top electrode is a wire ring. This construction allows the device to be used as a neon indicator - allowing a visual indication of the presence of the stabilised voltage.
A closer view of the construction. There is red paint on the outside of the glass at the top.
The thin glass tube envelope is 16 mm in diameter, and excluding the B7G base pins is 42 mm tall.