747 O2
As I recall, on the now-very-old 74s of the BA (ex-BOAC) fleet, Flight-Deck Crew have their own O2 bottles, and pax have further bottles (no O2 generators unless they have been subsequently installed.
In the event of Crew O2 failing, then they could "appropriate" the pax O2 (more important that the crew be fully-aware in an emergency!)