This is a barometric release mechanism was used by the British Royal Air Force to automatically deploy pilot parachutes at a safe predetermined altitude during high-altitude jumps or ejection. The condition is excellent with inside mechanism and the original wooden case Mechanism: Ref 15A/1509 Type: Barometric pawer unit Manufacturer: Irving air chute Co Model/ Type: Type B/2 Mk.2 RAF Reference number: 15A/1509 Serial number: 17247 Material: Metal, bacalite, wood Case dimension: 29×12×5 cm