The auction alleges the undergarments, which bear an embroidered crown and the letter "E," were left on an airplane when Elizabeth visited Chile in 1968 and ended up in the collection of Hungarian-born sculptor Baron Joseph "Sepy" de Bicske Dobronyi, who died in 2010, the British newspaper The Daily Telegraph reported Monday.
The description in the auction, which was purportedly posted by Dobronyi's estate, says Buckingham Palace and the manufacturer of the garment have refused to confirm or deny the authenticity of the item.
"In either case this is an excellent example of a vintage undergarment of that era and very collectible," the description says.
The auction, which ends May 22, had a high bid of $5,300 as of Monday afternoon.
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