The rare mystery clock is valued at $425,000 and was stolen from the stand of dealer MS Rau Antiques at the Chicago Antiques + Art + Design Show at the weekend.
Bill Rau, chief executive at MS Rau, said that although there was security throughout the show the thieves were able to take the item from the stand during the fair.
“It was unfortunate that this theft happened during what was otherwise a wonderful and successful show,” he said.
An investigation is under-way and security footage is being reviewed by the police.
Rau added: “We’re confident that the criminals will be quickly apprehended and this wonderful timepiece returned. We’re awaiting further details.”
It is expected the dealer could offer a reward for the item.
The fair was held on the seventh floor of the Merchandise Mart in Chicago. It is believed a couple distracted employees, while another stole the 18ct white gold clock which is encrusted with diamonds, sapphires, mother of pearl and crystal.
Mystery clocks are so-called because the hands of the clock appear to float without any working mechanism on display.