A Florentine court will rule on custody of a painting known as the ‘Earlier Mona Lisa’ on 9 September.

The hearing follows a request to impound the disputed work from Giovanni Battista Protti, a Padua-based lawyer. Protti represents a family who are said to own a 25% share of the portrait. He asked the Florence court and Italian Culture Minister Alberto Bonisoli to sequester the painting on the basis that it was imported to Italy and exhibited without the consent of his clients.

Also referred to as the Isleworth Mona Lisa, the painting depicts Lisa Gherardini, the wife of Florentine silk merchant, Francesco del Giocondo. Her likeness, by Leonardo da Vinci, is the jewel in the crown of the Musée du Louvre in Paris. The owners of the Isleworth Mona Lisa believe their painting is the earlier portrait, but other experts suggest it is a later copy of the Louvre work.

The Isleworth portrait has been stored in a Swiss vault since 1975. Found in a Somerset country house by English Art Collector, Hugh Blaker, he bought it and took it to his studio in Isleworth, west London. Blaker later sold it to British art historian, Henry Pulitzer, who sold a quarter share to Leland Gilbert, a Portuguese porcelain manufacturer. The lion’s share of the painting passed to Pulitzer’s partner and then an international consortium called the Mona Lisa Foundation.

Gilbert’s heirs, represented by Protti, are disputing the ownership of the Isleworth Mona Lisa. According to Protti, his clients were upset that the Mona Lisa Foundation did not consult them when they decided to exhibit the portrait this summer at Palazzo Bastogi in Florence. The exhibit formed part of events marking 500 years since the death of Leonardo da Vinci.

Protti explained that his clients were motivated by a desire to increase visibility of the portrait, which ordinarily resides in the Swiss vault. “Whoever owns it has a responsibility towards humanity. It’s important it should travel the world, for the benefit of everyone”, Protti said.

Mona Lisa Foundation representative, Markus Frey, stated that the claim by Protti’s clients is “ill-founded and has no merit”. Fellow Foundation representative, Jane van Lanschot Hubrecht, believes the claim may have been inspired by recent academic studies which suggest the Isleworth portrait can be attributed to Leonardo.

While the ownership dispute is set to be resolved next month, the attribution debate continues.