Nice Peter,
Put "Flitz" or "Semichrome" on the whole knife, all of it. Rub-n-rub-n-rub real hard...repeat several times. Get some Johnson's hard wax (in a can) for wood. It's really good for everything. Apply it to the entire knife, including the sheath, liberally and rub-n-rub-n-rub. You'll love the outcome and it won't ruin any collectablility.
Good luck with it, Capt. Chris
PS: You don't need the wax on the "rough" part of the roughback sheath...CCS