A normal air cane front half Barrel has a male thread that screws into the air reservoir, this is the other way around?
If you look at the air canes in the Library you can see this.
I would say this is a one off.
Im rather interested in just how the trigger mechanism works as a standard air cane trigger fires a pin into the air reservoir which knocks open a valve.
This one well without opening it up and taking a peek is a bit of a mystery!