forced to abdicate in Sima Yan's favor, passing the Seal from Cao to Sima and establishing the Jin dynasty in 265. Loss The Seal was passed through the Cao Wei Dynasty, Jin Dynasty, Sixteen Kingdoms period, Southern and Northern Dynasties period, Sui Dynasty and Tang Dynasty, but was lost to history in the Five Dynasties and Ten Kingdoms period (907-960). The fate of the seal during and after the Five Dynasties and Ten Kingdoms period is not known. Three theories exist as to when, and how, it was lost: At the end of the Later Tang, when the last emperor died by self-immolation. In 946 AD when the Emperor Taizong of Liao captured the last emperor of the Later Jin state. The seal came into the hands of the later Yuan emperors. When the Ming armies captured the Yuan capital in 1369, it captured just one out of the eleven personal seals of the Yuan emperors. The Heirloom Seal was not found. In 1370, Ming armies invaded the Northern Yuan dynasty and captured some treasures brought there by the retreating Yuan emperor. However, once more the Heirloom Seal was not found. By the beginning of the Ming Dynasty, the Seal was known to be lost. Neither the Ming nor the Qing dynasties possessed it. This partly explains the Qing Emperors' obsession with creating numerous imperial seals – for the emperors' official use alone the Forbidden City in Beijing has a collection of 25 seals – in order to reduce the significance of the Heirloom Seal. In the early 20th century, as the Qing Empire pursued reforms to modernise its system of government, a series of official seals were created for use on documents and instruments of the imperial government. Although square in shape following the traditional design, the seal dies themselves were made of wood, in imitation of western government precedents and, contrary to earlier Qing imperial seals which were bilingual (Chinese and Manchu), had only Chinese text. Four seal dies were carved: "The Seal of the Great Qing" (大清國寶), "The Seal of the Great Qing Emperor" (大清皇帝之寶), "The Great Seal of the Great Qing Empire" (大清帝國之璽), and "The Seal of the Emperor of the Great Qing Empire" (大清帝國皇帝之寶). Of these, the Great Seal of the Great Qing Empire represented the official, modern "replacement" for the lost heirloom seal. The seal dies are in the collection of the Palace Museum