This is the Model 31. Acetylene is produced in the generator can from carbide and is fed to the
muzzle via a rubber tube. The pistol grip is attached to a plunger inside the barrel. Pushing it
all the way forward expels spent gas and cocks the internal flint striker. Drawing the handle back
pulls in gas and air. Pulling the trigger fires the charge and the drill is repeated.
Click here for Smith's 31 Instructions