Tiffany & Co's unset Empire Diamond in its design stages. Image: Tiffany & Co

Tiffany & Co's Empire diamond set into a ring that could be separated from the neckpiece to form two distinct pieces of jewellery. Image: Tiffany & Co

World’s Fair Necklace from 1939 was when The Empire diamond first made its original Tiffany & Co. debut. Image: Tiffany & Co.

Tiffany's reimagined World's Fair Necklace is valued at between US$20 million and $30 million.

Victoria Reynolds, chief gemmologist Tiffany & Co