Coster Diamonds Factory, Amsterdam

The oldest diamond polishing plant in the world, Royal Coster Diamonds Factory, is located in Amsterdam, Netherlands. They have handled a few historical treasures since their founding in 1840. They re-polished the Koh I Noor, which is mounted in Queen Mary’s crown, and the Dresden Green Diamond, which is kept in Dresden Castle’s New Green Vault.

Mr J.A. Feder and Mr L.B. Voorzanger, both diamond polishers from Royal Coster Diamonds, traveled to London in 1852 to repolish the legendary Koh-i Noor. In 1864, Mr. J.A. Fedder passed away. At the 1855 World Exhibition in Paris, Louis Benjamin Voorzanger received a silver medal for his achievements.

He was also in charge of polishing the “renowned diamond Star of the South.” In 1886, he passed away. The silver plates with the inscription of this fee for the diamond polishers who polished the Koh-i Noor are still owned by the family of the deceased diamond polisher.

Ben Meier polished the numerous diamonds placed in a white gold watch that the Dutch people presented to Queen Juliana in 1959. Pauline Willemse, a diamond polisher at Royal Coster Diamonds, polished the world’s tiniest diamond between 1991 and 1994. This is a 0.0000743 carat brilliant cut stone with 57 facets (0.01486 mg). With a diameter of 0.16–0.17 mm and a height of 0.11 mm. The Guinness Book of Records recognized this achievement. This and other notable diamonds may be seen during a diamond tour of the polishing plant at Royal Coster Diamonds.