Meteor T.7 Question.

On the Port side of the Gloster Meteor T.7 rear cockpit, there are three oxygen cylinders, and behind them on the floor, an Oxygen ecconomiser. Between the Oxy cylinders and the ecconomiser is provision for what looks to be another, possibly larger cylinder.
Can anyone tell me what that cylinder is please? or does anyone have photo’s of Meteor T.7 cockpit’s showing detail?
Thanks in advance.