As good as it can be set-up an a database or card system; the problem of tracking these items is a real nightmare - thats why most airlines do carry out physical inventory checks as regularly as possible.
I would question any QA engineer who finds all the emergency equipment on a line aircraft, exactly as it is supposed to be from computer printouts. Portable Oxy bottles seem to be changed all the time, Vests go 'missing' (normally stolen) and if found missing (I've always worried about that phrase) replaced.
All are often replaced/installed in Ship-Sets to give some indication of control, but invariably items are changed or lost.
This wont help - but its all there is!