This is an instrument for testing cans after both ends have been   seamed on, to ascertain leaks in either the body or the end.

  To operate, the pointed portion of the spike is pushed into the   can and rotated slightly. The lever on the side of the tester body   is depressed to compress the rubber gasket to form an airtight   seal. Air is then forced into the can, trough the air value, by   means of the hand pump provided, to a pressure of 12 to 15 lbs per square inch (0.84 to 1.05 kg per square centimeter approx).   After which the can is impressed in water to indicate the position   of any leaks.