The CV6173 is a gas filled triggered spark gap modulator known as a trigatron. The commercial equivalent is the 24B9.
The fabric basket sealed in resin was required as these devices had a habit of shattering during use. The pulse power switched into a magnetron by the 24B9 was of the order of 160 kW.
The UK's first atomic bomb was an implosion device and the 32 explosive segments had to be triggered simultaneously. Bridge wire detonators were used fired by a high voltage high current pulse. A trigatron was used to discharge the capacitors into the detonators. See the attached pdf pages 44 and 45.
A pinch construction at the base with the anode supported from the top cap.
There looks to be a shield plate above the anode.
The open base with two stranded wires.
The original box. The valve was wrapped in plastic foam. The box measures 117 mm square and is 256 mm tall.
The label over the box end. The date is 2nd February 1973.
The wide glass tube envelope is 68 mm in diameter and, including the base pins, is 150 mm tall.
Reference: Data-sheet. Type CV6173 was first introduced in 1971.