It is because the dial of the watch is not made of ordinary material, but of mother-of-pearl, a natural mother-of-pearl that is a colorful and illuminating substance that covers the inner surface of the shells of certain mollusks, and is especially used to make dials and cases, etc. The dial of the watch is made of mother-of-pearl, which is a natural material. Artificial mother-of-pearl is made from the scales of fish and animal horns. Mother-of-pearl has a creamy, lustrous color. Some watch dials are made of mother-of-pearl, which is more durable and does not change color.