A marble sculpture of the head of French queen Jeanne de Bourbon is set to sell at Paris auction house Piasa on December 11.
The piece was created in the 14th century, and is believed to depict Jeanne de Bourbon, wife of King Charles V. It has been attributed to Flemish sculptor Jean de Liege, and is expected to sell for between $614,000-1.2m.
However, it could be worth far more. Liege was known for his work on funerary monuments, and the head could be an incredibly valuable missing piece from the queen's tomb, which was vandalised during the French revolution.
With the Louvre and New York's Metropolitian Museum of Art interested, bids are likely to rise far past estimate as the institutions compete for the right to conduct further scholarly research.
The sculpture has come to auction from a Belgian industrialist, who has owned it for more than 50 years.
The queen died in 1378, having taken a bath; ignoring her doctor's advice while pregnant.
She went into labour shortly afterwards and died two days later. Her heart and entrails were buried at separate locations according to the tradition of the day, but her body was interred at the Basilique Saint-Denis.
Please sign up to our free newsletter for more exciting news about antiques auctions.