A hallmark is a distinctive characteristic of something or someone. That can mean a literal symbol on the bottom of a piece of pottery, or just a rock star's signature hair style.
Though some products have real hallmarks on them, indicating their creator or origin, this word is usually used in a less literal way to describe a unique attribute, a special style, or typical feature. A basketball player could say that coming to practice early is a hallmark of her success. A business could say their success is a hallmark of their commitment to customers. And you could definitely say Elvis' hip swivel was a hallmark of his performances.