 However, the historian of Korean cartography, Gary Ledyard, argued that this device could not have been made as early as 1669, since the names given on the map of the earth on the terrestrial globe at the centre of the object shows a name for part of the southern continent that could not have been known in Korea at that period.More recently, O Sanghag 오상학 has argued that the object may date from as late as the beginning of the 19th century, in the time of Crown Prince Ikjong 익종 翼宗 (1809-1830), before the prince became regent in 1827.An image of the clock's sphere is shown on the reverse of the 2007 issued 10,000 won banknotes