8．The most controversial piece: Gong Fu Tie

The seal on the allegedly authentic Gong Fu Tie calligraphy is magnified by a museum employee. [Photo/IC]

The controversial calligraphy piece, Gong Fu Tie, was composed by Chinese writer and calligrapher Su Shi (1037-1101) during the Northern Song Dynasty (AD 960-1127).

Chinese collector Liu Yiqian bought it back from a Sotheby's auction in New York for $8 million in September 2013.

Then on December 21, however, it was reported by the Xinmin Evening News that three experts from the Shanghai Museum alleged the work was a replica, made during the late Qing Dynasty (1644-1911).

Therefore, two months after the Shanghai Museum's claim of the piece as a fake, Liu and his Long Museum confirmed the authenticity of the work at a news conference in Beijing in February.

By applying high-definition technology to examine the writing characteristics, the paper itself and the seals found on the work, and inviting different experts to appraise the calligraphy, Huang Jian, the executive curator of the Long Museum, verified its authenticity along with Liu Yiqian.

Related: Controversial piece has art world in a flap