Good question. I think of the natural leathers as the ones that will absorb oil, water, etc. Box has a somewhat water/ oil repelling finish to it. I think natural vache and chamonix would be closest look to natural box. I like the leathers that have to be imprinted rather than painted with the "Hermes"
Maybe a leather expert will respond.
I'll try to remember to check leather book next time I visit H.