One thing I can't help but mention is the fact that unsealed steel will rust .
Oiling will of course prevent this , but just like a gun , if someone touches the oiled steel , oxidation begins .
Oiling & waxing surfaces tend to grind dust & such into surfaces & do build up a patina through their use .
If an item is truly ancient , waxing & oiling wood is a no-no ("if it's dead , it don't need to be fed") for the experts .
For practical use , hey , we gottta use what works .
I'm going to give one opinion , (from an "antique heretic's" point of view) , that you might consider putting a coating on the meal & wood of your trunk .
I have seen so many bad shellac jobs done on trunks of this genre that I cringe at suggesting so .....
I've had very good results with a couple/three coats of 50/50 mixed laquer (50% laq. thinner) .
When fully dry , I degloss the surface to a nearly-matte finish & don't have to worry about rust (or doing real tough touch-up work on new dings & such) .
I did a matching pair for a buddy 35yrs. ago that are still 'looking good' .