New brass is loud. Mirror-bright, a little showy, trying hard. Left alone, it calms down — the shine softens, the tone deepens, and it slowly starts to look like it belongs to you.
That's patina, and most brass products fight it with a thick lacquer that freezes the factory shine in place forever. We mostly don't. The torans and coasters are meant to age.
If you love the bright look, a minute with a cloth and some polish brings it right back. If you love the softened one, do nothing — the more honest option, and free.
It's the rare object that improves while you neglect it. Enjoy that. It is not going to happen with your phone.