Plating identification question

["Vito Pacione" <vito@argohouston.com>]

Does anyone know what the plating used on the spare hold down hook (the one
that goes through the frame cross member and up through the body) might be?

It looks duller than black zinc, but shinier than an oxide. I don't know
what parkerizing looks like and I'm wondering if that's not what it might
be.

It looks like a nice semi-gloss, almost an oiled finish.

Thanks!