Three art historians who are affiliated with the state-run Shanghai Museum are saying that Sotheby’s sold a fake Chinese scroll for $8.2 million last September. ‘Gong Fu Tie,’ which soared past its high estimate of $500,000, was listed as a thousand-year-old masterpiece of Chinese calligraphy by Song Dynasty poet, Su Shi.

The historians are saying that the work, which was purchased by Shanghai businessman and collector, Liu Yiqian, was produced during the 19th century using an old method for copying and retracing artworks. The experts also stated that the forgery was made using a stone carving rather than the original work.

Sotheby’s released a statement saying that the auction house “firmly stands by the attribution of ‘The Gong Fu Tie Calligraphy’ to the Song Dynasty poet Su Shi.” If the scroll is deemed a forgery it could be a major blow to Sotheby’s, which is trying to expand its reach in China and touting its high standard of expertise to collectors both in and outside of the country.