samples of the gun, specifically the hand cannon (huochong), have been dated starting from the 13th century. The oldest extant gun whose dating is unequivocal is the Xanadu Gun, so called because it was discovered in the ruins of Xanadu, the Mongol summer palace in Inner Mongolia. The Xanadu Gun is 34.7 cm in length and weighs 6.2 kg. Its dating is based on archaeological context and a straightforward inscription whose era name and year corresponds with the Gregorian Calendar at 1298. Not only does the inscription contain the era name and date, it also includes a serial number and manufacturing information which suggests that gun production had already become systematized, or at least become a somewhat standardized affair by the time of its fabrication. The design of the gun includes axial holes in its rear which some speculate could have been used in a mounting mechanism. Like most early guns with the possible exception of the Western Xia gun, it is small, weighing just over six kilograms and thirty-five centimeters in length. Although the Xanadu Gun is the most precisely dated gun from the 13th century, other extant samples with approximate dating likely predate it. One candidate is the Heilongjiang hand cannon, discovered in 1970, and named after the province of its discovery, Heilongjiang, in northeastern China. It is small and light like the Xanadu gun, weighing only 3.5 kilograms, 34 cm (Needham says 35 cm), and a bore of approximately 2.5 cm. Based on contextual evidence, historians believe it was used by Yuan forces against a rebellion by Mongol prince Nayan in 1287. The History of Yuan states that a Jurchen commander known as Li Ting led troops armed with hand cannons into battle against Nayan. It reports that the cannons of Li Ting's soldiers "caused great damage," but also created "such confusion that the enemy soldiers attacked and killed each other." The hand cannons were used again in the beginning of 1288. Li Ting's "gun-soldiers" or chongzu () were able to carry the hand cannons "on their backs". The passage on the 1288 battle is also the first to coin the name chong () with the metal radical jin () for metal-barrel firearms. Chong was used instead of the earlier and more ambiguous term huo tong (fire tube; ), which may refer to the tubes of fire lances, proto-cannons, or signal flares. Even older, the Ningxia gun