This wall mounted fire extinguisher was hung near furnaces and other combustible areas.  These is a spring loaded small hammer with a fusible link on the bottom.  The fusible link would melt from the heat of a fire causing the hammer to swing around and break the glass container allowing carbon tetra chloride fluid to splash on the fire.  The unit could also be thrown at the base of a fire by hand thus breaking the glass to extinguish the flames.