Marzo platinum, diamond and natural pearl bar brooch of royal interest, £55,000 at Young’s Auctions.

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They came by descent from Mary, Princess Royal and Countess of Harewood (1897-1965), the only daughter of George V and Queen Mary.

The countess is believed to have received this Belle Epoque brooch as a gift from the Duke and Duchess of Windsor. Made by the Paris jeweller Marzo, and in its original blue tooled leather case, it comprises three natural pearls set in platinum and diamonds.

According to the report from the Gem and Pearl Laboratory, the central pink gem, is a 14mm natural conch pearl, flanked by a natural iridescent grey pearl and a natural cream-white pearl.

Estimated at £8000-12,000, it took £55,000.

Lorenzo Marzo, the nephew of Spanish court jeweller Francisco Marzo, set up his own business in Paris in 1901, trading from 207 rue St Honoré and then 22 rue de la Paix under the banner Laillet et Marzo.

Conch pearls occur naturally only and cannot be commercially cultured. It is estimated that they are found in only one in every 15,000 conch shells with a large, near-spherical example like this a great rarity.