In the trilogy, The Lord of the Rings, Tolkien describes Sauron's fortress of Barad-dûr as having a high tower, within which there exists the Eye of Sauron.
In the black abyss there appeared a single Eye that slowly grew, until it filled nearly all the Mirror. So terrible was it that Frodo stood rooted, unable to cry out or to withdraw his gaze. The Eye was rimmed with fire, but was itself glazed, yellow as a cat's, watchful and intent, and the black slit of its pupil opened on a pit, a window into nothing.
[The Fellowship of the Ring, Book II, Chapter 8]
And throughout the story, there are scattered references to the lidless eye in connection with Sauron. The Lord of the Nazgul, for instance, warns Dernhelm -
'Come not between the Nazgûl and his prey! Or he will not slay thee in thy turn. He will bear thee away to the houses of lamentation, beyond all darkness, where thy flesh shall be devoured, and thy shriveled mind be left naked to the Lidless Eye.'
Frodo physically possesses an Elven artifact, the Ring, which confers upon its bearer a power to see things from far away, as he experiences upon Amon Hen at the conclusion of Book II. In The Two Towers Sauron, Saruman and Denethor all possess Elven artifacts, the surviving palantíri, which confer upon their keeper a power to see far away. Gandalf refers to other Elven artifacts of power, the Silmarils stolen by Morgoth in the First Age; and he turns out to possess, himself, one of the Three Rings of the Elven Kings. And Galadriel has yet another Elven artifact with the power to see far away: namely, the Mirror of Galadriel.
Is the Eye of Sauron an Elven artifact, obtained or stolen by Sauron in the Elder Days? Like the Ring, it evidently confers a power to see far away (for Sauron uses it thus, at a time when he no longer possesses the Ring). But I am not as familiar with The Silmarillion, or Unfinished Tales, or The History of Middle Earth, or The Letters of JRR Tolkien as I am with the trilogy.
I am not asking whether the Eye is a real object rather than a metaphor. For myself, I am satisfied that it is not a metaphor, for Frodo sees it as an actual object, in the Mirror of Galadriel: in the passage I have quoted above, both the Mirror and the Eye appear to be real objects having a physical existence.
Is there evidence, anywhere in the writings of Professor Tolkien, which casts light on the nature, or origin, of the lidless eye? Is it in fact an artifact? If so, is it Elvish in origin (like the Silmarils, the palantíri, the Mirror of Galadriel, and the Elven Rings)?
Is there any suggestion that Sauron's power to see far away derives simply from his possession of the Ithil Stone (rather than being an innate power of the Eye of Sauron)?