Take a lock at this picture!

What is that plate between the rod and the coil and what dose it do? :?:

Its a inductor from a radio.

PS:
I think thats a ferrite plate. :?

This is only some isolator for wire-end fixing (e.g. paper) The manufacturer don't made the coil direct to ferrite rod with machine. The other cause: with this method You can find the best place of coil on ferrite rod. (tuning)