May i doubt that an item made of plain iron stays stable, out of rust; you should see how fast rust atacks in humid environments ... like in mine, for one. Besides, i guess, oiling a piece gives it a less dull look ... and does no harm, i'd say.
I agree that giving this cabasset an original look by adding back countless components might be senseless but, recreating a sole detail like a
PLUME HOLDER would give it back some grace
.
... And you may of course take month to reach for decision ... right Ken ?
.