The 24B9 is a gas filled triggered spark gap modulator known as a trigatron. The fabric basket sealed in resin was required as these devices had a habit of shattering explosively 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.
The base is also marked as CV9173.
The the triangular sockets on the base will accept 4 mm plugs.
The wide glass tube envelope is 68 mm in diameter and, including the base pins, is 152 mm tall.
Reference: Data-sheet. Type 24B9 was first introduced in 1971.