I'm sorry to resurrect this thread but I used to work for AP up until about five years ago. That cylinder in the picture was a current one and there are still thousands out there. They were slowly repainting them all in the new grey/green colours as they came in for safety checks. The sticker on them with the numbers on is the stock code, there's two, one's a full code the other empty. They were experimenting with individual bar codes so each cylinder could be tracked(thus avoiding people acquiring cylinders and getting them refilled at a mate's engineering works ), but I don't know if they have actually implemented it yet. Anyone know???