Om is the sound and the vibration by which the universe was created, and thus represents the vibrations of all things in the universe.

In the Mandukya Upanishad:

"Om" is the eternal word; what was, what is, and what shall be. It is All.

The curves of the sanskrit letter are representative of the three states of consciousness: the waking state, the dream state, & deep, dreamless sleep. When we pass through the sheath of maya, or illusion, (the cresent shape), we reach the state of union (the dot) with Brahman.

Made of Brass.