The CV1949 is a miniature thyratron. The prototype was the 6D4 that also appears on the glass.
The box anode hides the internal structure. The dark metal screen/heat sink below the double mica discs connects to the control grid. Double mica discs are used to strengthen the construction to ensure a long life in applications subject to shock and vibration.
The electrodes seen end on. The grid has a similar screen/heat sink at the top.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 46 mm tall.
