The woman had jewellery to sell: diamond bracelets and rings with precious stones in 18-carat gold, and other items that she said were hers "and free of any legal encumbrances", according to a form she signed.
What the woman, a Tiffany & Co vice-president, did not disclose was how the jewellery managed to become free of legal encumbrances.
US authorities said Ingrid Lederhaas-Okun, 46, took valuables from Tiffany and then effectively wrote them off the company's books, using a practice that allows items to be cancelled from inventory under certain circumstances.
The executive was arrested at her home in Darien, Connecticut, on Tuesday on charges of wire fraud and interstate transportation of stolen property, prosecutors said.
Lederhaas-Okun and her husband were paid about US$1.3 million by a leading New York buyer and reseller of jewellery, before it was discovered that she had been selling Tiffany merchandise, the authorities said.
They said Lederhaas-Okun had lost her job as vice-president of product development at Tiffany in February as part of an overall company downsizing. Tiffany then conducted an inventory review, showing that, since November last year, she had checked out about 165 pieces of jewellery with a retail value of US$1.2 million.
It was the company's practice to count every item worth more than US$25,000 each day that it was checked out, a policy of which Lederhaas-Okun would have been aware, the authorities said. Each piece of jewellery that she had checked out was valued at less than US$10,000.
A criminal complaint filed in the US District Court in Manhattan says that most of the more than 200 pieces of jewellery sold to the reseller matched the description of items that Lederhaas-Okun had checked out while working at Tiffany and were missing from its inventory.
"Ingrid Lederhaas-Okun went from a vice-president at a high-end jewellery company to jewel thief," said Preet Bharara, the US attorney in Manhattan. The charges were announced by Bharara and George Venizelos, head of the FBI's New York office.
Lederhaas-Okun was released on bond by a federal magistrate judge on Tuesday. Her lawyer declined to comment.
A Tiffany & Co spokeswoman said: "In deference to the US attorney's investigation, we are not in a position to comment at this time."
According to the complaint, Lederhaas-Okun's job duties included ensuring that product designs could be manufactured, and in that role she was allowed to check out jewellery for work-related reasons, such as showing it to potential manufacturers to determine production costs.
She was also able to "write off" or cancel the cost of jewellery that had been rendered unusable, the complaint noted. Usually such items were returned to the company's stock and destroyed, the complaint noted.
The jewellery she checked out included diamond bracelets in 18-carat gold, platinum or gold diamond drop-and-hoop earrings, platinum diamond rings, and platinum and diamond pendants, the authorities said.