PARIS (AFP) ― An association for the protection of Chinese art on Sunday warned it would pursue legal action if a French auction house goes ahead with the sale of an imperial seal it says was looted.

The Association for the Protection of Chinese Art in Europe (APACE) urged auction house Artcurial to withdraw the jade green seal, dating from the Qianlong period (1736-95), from its auction on Monday.

It said the seal, expected to fetch up to 200,000 euros ($263,000), was stolen during the sacking of the Summer Palace in Beijing by Anglo-French forces in 1860.

The group said it had already mandated a lawyer to “take all legal action,” including filing a criminal complaint for theft and receiving stolen goods, if the sale goes ahead.

Artcurial denies the seal is from the Summer Palace and says this has been confirmed by Laurent Long, the world expert in seals.

The catalogue listing for the seal states it is from “a French private collection and in the same family since the late 19th century.”