 A reduced "Regnum Italiae", a heritage of the Lombards, continued to exist for centuries as one of the constituent kingdoms of the Holy Roman Empire, roughly corresponding to the territory of the former Langobardia Maior.The so-called Iron Crown of Lombardy, one of the oldest surviving royal insignias of Christendom, may have originated in Lombard Italy as early as the 7th century and continued to be used to crown Kings of Italy until Napoleon Bonaparte in the early 19th century.The earliest Lombard law code, the "", may allude to the use of seal rings, but it is not until the reign of Ratchis that they became an integral part of royal administration, when the king required their use on passports.