That which was for the head
to hold the lights
was that which was for the neck
to hold the life.
The Iron Crown
The Iron Crown (for the head) was made by Morgoth to hold the Silmarils (to hold the lights) was made into his collar (was for the neck) after the War of Wrath. (Source: the Silmarillion)
(Do you include "The" in the answer?)
Tolkien Gateway: Iron Crown