Acrylic crystal

An acrylic crystal is a plastic dial cover, common on older watches and still used on some models, sometimes under trade names such as Hesalite.

It scratches easily but can often be polished back to clear, and it tends to crack rather than shatter. On vintage references, collectors usually prefer the original acrylic over a sapphire replacement.

Light scratches on acrylic are usually a minor, cheap fix. Note deeper cracks, which need a replacement.

Because acrylic is lighter and slightly domed on many older references, a sapphire replacement can change how the watch looks from the side, which is another reason collectors notice it.