A rare pink diamond stolen from a French château almost a century ago has gone back on public display, with the story of its theft and recovery as the centrepiece of a new exhibition.

The nine-carat, pear-shaped stone, known as the Grand Condé, was taken in an overnight raid on the Château de Chantilly in October 1926. The thieves hid it inside a hollowed-out apple. It was found a few weeks later when a hungry maid at the hotel where they were staying bit into the apple, the museum says.

The diamond is now being shown at the Condé Museum inside the château, about 50km north of Paris, until 3 January. Museum director Mathieu Deldicque said the story of the recovery may sound far-fetched, but it was widely reported in newspapers at the time.

The exhibition opens as European museums face renewed questions about security after a string of high-profile thefts in the past year, including a daylight robbery of jewellery from the Louvre in Paris. Deldicque declined to say how much the Grand Condé is insured for, but said extensive research had been done so that the stone can be identified by its distinctive properties.

The show brings together the findings of that research and previously unseen archive material about the gem's history and its theft. Its exact origins remain a mystery. It was first recorded in 1740, in an inventory drawn up after the death of Louis Henri de Bourbon, Prince of Condé, and later passed through the collections of Queen Marie-Amélie and her son, Prince Henri of Orléans, the Duke of Aumale, who left it to the Institut de France along with the rest of the Musée Condé collection.

Naturally occurring pink diamonds are very rare and can sell for tens of millions of dollars. The highest price paid for one at auction was $71.2m in 2017, according to Sotheby's.