A diamond brooch taken from Napoleon Bonaparte following his defeat by Prussian forces in 1815 has fetched $4.4 million at Sotheby’s Geneva—exceeding its highest pre-sale estimate by more than seventeen times.The piece, which converts into a pendant, showcases a 13.04-carat oval diamond encircled by nearly 100 old mine-cut diamonds set in two rings. Initial estimates had valued it between $150,000 and $250,000.

According to Sotheby’s, Napoleon was forced to leave behind several carriages, including one carrying valuable possessions, when they became mired in mud several miles from the Waterloo battlefield as he rushed to escape the combined British and Prussian forces that had defeated his army.

The brooch was given to Prussian King Friedrich Wilhelm III three days after the battle as a war trophy. It stayed within the Hohenzollern dynasty for generations, passing through various German emperors, before entering a different private collection in recent years.

Another Napoleonic treasure, a 132.66-ct green beryl which he is reported to have worn on his coronation mantle in 1804, was bought for $1m by a US museum – also for 17 times its high estimate.Both items were highlights of the Royal and Noble Sale, which raised a total of $14.3m.