You are buying a re-manufactured Sparklets Soda syphon spare/ accessory.
This listing is for a combined CO2 capsule plastic charger/bulb holder and neck sleeve removal tool and is designed to be used with the Sparklets/BOC Hostmaster Mark. 3 model of soda syphon. The original versions of these were marketed in the period of 1967- 1981 and were supplied for the Hostmaster Mk. 3 range of syphons. Unfortunately, the original versions were not particularly good for removing the pale/translucent plastic neck sleeve in order that the insides could be conveniently cleaned out. An improved version has now been re-made which better locks into the tops of the neck sleeves found in the Hostmaster Mk. 3 syphons. These are made of black plastic and have a cleverly shaped tool built into them for removing the plastic neck sleeve of Hostmaster and the stainless Ambassador style syphons of similar shape. Simply insert the T shaped part of the top end of the key into the wider part of the slot on the top of the neck sleeve, rotate by about 90 degrees to engage the arms of the tool with the flange on the inside of the sleeve and lift out.
See my other listings for period accessories.
P. S. If you happen to have a Sparklets soda syphon that you would like reconditioning, please see my other listings.