agency and commercial corporation has its own seals to use in public documents. While signing is also accepted, many Koreans think it is more formal to use seals in public documents. In 2008, the Constitutional Court of South Korea upheld a Supreme court judgement that a signed handwritten will without a registered seal was invalid. Korean seals are made of wood, jade, or sometimes ivory for more value. State Seals were generally made of gold or high-quality jade. There are rare cases of bronze or steel seals. Mongolian usage While Chinese-style seals are typically used in China, Japan, and Korea, they are occasionally used outside East Asia. For example, the rulers of the Ilkhanate, a Mongol khanate established by Hulagu Khan in Persia, used seals containing Chinese characters in their diplomatic letters, such as the letter from Arghun to French King Philip IV and the letter from Ghazan to Pope Boniface VIII. These seals were sent by the emperors of the Yuan dynasty, a Mongol-ruled dynasty of China, especially by Kublai Khan and his successor Emperor Chengzong. Personal seals Personal seals () in Korea can be classified by their legal status. Ingam (인감, 印鑑) or sirin (실인, 實印), meaning registered seal, is a seal which has been registered by a local office, attested by a "certificate of seal registration", () a document required for most significant business transactions and civil services. The legal system of registered seals was introduced by the Japanese colonial government in 1914. While it was scheduled to be completely replaced by an electronic certification system in 2013 in order to counter fraud, ingam still remains an official means of verification for binding legal agreement and identification. The government passed the 'Act on Confirmation, etc. of Personal Signature (본인서명사실 확인 등에 관한 법률)' in 2012, which gives registered handwritten signatures the same legal effect as ingam. While ingam is used on important business, other dojangs are used for everyday purposes, such as less-significant official transactions. Thus most Koreans have more than two seals. In traditional arts, as in China and Japan, an artist of Chinese calligraphy and paintings would use seals (generally leisure seals and studio seals) to identify their work. These types of seals were called Nakkwan (낙관, 落款). As seal-carving was also considered a form of art, many artists carved their own seals. Seals of Joseon-period calligraphist and natural historian Kim Jung-hee (aka Wandang or