Original Aerators brand Carbon dioxide capsule/charger key, manufactured from around the 20's to the early 30's, and designed to fit the early Aerators Limited Type C "Prana" mesh covered glass bodied soda syphons (although this key will fit any Sparklets syphon from the 1920's through to the 1980's).  Produced in an unusual light-weight "silvery" die-cast Aluminium-zinc alloy and designed to fit the C (8 gram) sized CO2 capsule, which remains widely available to this day.   As this was produced when the Type C was still in production by Aerators Limited  it is of a slightly different design to the later Sparklets keys, and features a back mounted rib which leads to its commonly held name of a "rocket shaped charger key".