WW2 Field produced Soldering Tool

This fascinating item appears to be a field produced soldering or braising tool, consisting of a wad filled copper tube set inside a 1942 dated 20mm cannon shell case. Presumably the shell case would have been filled with petrol? Which would have burned through the wad or wick forming a very hot base on top of the tube. The external tube would have allowed the introduction of oxygen? to increase the temperature of the burn. A superb example of 'Tommy' ingenuity in the field.