They're almost certainly chrome, it's pretty hard to get nickel Tele knobs, control plates or neckplates (Allparts have them, though).
As far as I know, there's no easy way to "relic" chrome - it doesn't naturally tarnish like nickel, and I don't think it reacts to acids like nickel does. All you can do is scratch/dull the surface with wire wool or something.
But I could be completely wrong! Someone should come along with better advice.