The CV2224 is a gas filled trigger tube and functions in a similar way to a thyratron in that a control voltage at a critical level will initiate an ionization of the gas across the main gap and cause a rapid breakdown of the gap resistance.
The priming cathode is on the far left with the priming anode the next sheet of metal to the right.
The priming cathode seen under the STC logo.
The STC commercial Type designation G1/371K is also on the glass.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 44 mm tall.
Reference: Datasheet. Type CV2224 was first introduced in 1955.