Coster Diamonds is one of the oldest still operating diamond polishing factories in Amsterdam, Netherlands. They were responsible for the creation of a few historical masterpieces, like the re-polishing of the Koh i Noor, mounted in the Crown of Queen Mary, to be admired in the Tower of London, amongst the other Crown Jewels of the United Kingdom and the Dresden Green Diamond, which belongs to the Saxon dynasty.
In 1852, Mr J.A. Feder and Mr L.B. Voorzanger, both diamond polishers at Coster Diamonds in Amsterdam, left to London to re-polish the famous Koh-i Noor. Mr J.A. Fedder died in 1864. Louis Benjamin Voorzanger won the silver medal for his achievements at the World Exhibition in Paris in 1855. He also polished the “Star of the South”. He died in 1886. The family of the deceased diamond polisher still owns the silver plates with the inscription of this price for the diamond polishers, who polished the Koh-i Noor.
Ben Meier polished in 1959 the many diamonds which were set in a white gold watch, which was presented to Queen Juliana by the Dutch people. Between 1991 and 1994 Pauline Willemse, a diamond polisher at Coster Diamonds polished the smallest diamond in the world, a stone with 57 facets, weighing 0.0000743 carats (0.01486 mg). 0.16–0.17 mm in diameter and with a height of 0.11 mm. This event was published in the Guinness Book of Records.