If it's an ancient lens, it had none originally. And single coatings are available. I can't remember now the Leica guy who could repolish and redo the coatings on the older Leica lenses as part of his repairs/restorations. He would recoat any lens.
Oh, yeah? I'd sure like to hear more about this. Certainly there's a way to do this without a jillion dollars worth of equipment.