One known and surviving use. It is possible that it exists in other places, since the vast majority of the planet's written work has not been digitized. It may also have been used other places that have not survived.

Just because it's not important to you does not mean it is not important.

The fact that is survived for 600 years makes it interesting and worth saving. It is infinitely unlikely that anything you do, write, or say will last that long.