Relatives of India's first president have sought the intervention of the country's ambassador to Switzerland to halt the sale of a rare watch once owned by him.
The great-grandson of Rajendra Prasad has written to the embassy in Geneva, requesting it step in and ensure the 18-carat pink-gold Rolex Oyster is returned to India.
The auctioneers insist the watch is being sold legitimately and estimate it will fetch up to £140,000.
In an email to the Indian ambassador in Switzerland, Ashoka Jahnavi Prasad said his family had only just discovered the watch had emerged decades after they last saw it, and were anguished by its sale.
"We have no idea how the watch reached Geneva but can confirm that the family had nothing to do with it," he wrote. "We also believe the item rightly belongs to the nation, to which we shall remain forever indebted for enabling our forebear to serve it... we should all feel most grateful if you could kindly look into the matter."
Mr Prasad, 56, told i that his great-grandfather, a humble man, only wore the watch on special occasions.
He said that following his great-grandfather's death in 1963, many of his possessions were donated to a museum in Patna, capital of the state of Bihar. He said that at some point in the 1960s, the watch "mysteriously disappeared".
He added: "We accepted the fact that we would never see it again. Then we read about this sale."
The watch is due to be put on sale on 13 November by Sotheby's, as part of a larger lot of timepieces. A spokesman, Matthew Weigman, said the seller of the watch wished to remain anonymous. He said there had been no contact from either the Indian embassy or a member of Dr Prasad's family.
He added: "Sotheby's had followed all of its customary due diligence procedures before accepting the watch for sale, including checking the consignor's title. Sotheby's established that the watch had never been reported as stolen to the Art Loss Register, the database of missing or stolen art."
A nationalist campaigner who served for 12 years as president, Rajendra Prasad is a revered figure in India, celebrated for his role in helping secure the country's independence along with Mahatma Gandhi.