Specialists at auction house Sotheby’s believe Nelson either acquired the pocket watch or he received it from an admirer following his the Battle of the Nile in 1798 and that he carried it during Trafalgar.
Nelson was killed after a French sniper’s bullet pierced his shoulder and shattered his spine during the battle and this pocket watch was removed while he was on the flagship HMS Victory.
Having been kept in private collections until now, it is being auctioned with an estimate at £250,000-450,000.
Daryn Schnipper, chairman of Sotheby’s international watch division, said: "The perfect timing of the British assault at the Battle of Trafalgar was key in the historic victory of the Royal Navy, so to be able to offer for sale the watch that Nelson probably used to establish the timing for this decisive battle is a real privilege."
The Emery pocket watch No. 1104 is now mounted in a gilt-brass carriage clock case and was made by Georgian watchmaker Josiah Emery (c.1725-97).
Even without the Nelson provenance the watch would be valuable as Emery, a Geneva watchmaker who set up in London, is renowned for his fine timepieces.
When Nelson died this watch was one of nineteen objects returned to Nelson’s mistress, Emma, Lady Hamilton, following his death. It was then inherited by the admiral’s brother, William, 1st Earl Nelson, and subsequently passed to his sole surviving child, Charlotte. She arranged for the watch to be mounted in its current form as a carriage clock.
The watch, which has previously been on loan to the Maritime Museum in Greenwich, had remained under the ownership of Charlotte’s descendants until it was bought by a private collector in the US. It is now being auctioned following the collector’s death last year.
It was not part of the sale of Nelson artefacts sold in July 1895 and acquired for the nation by the British government. It is now one of only a small handful of Nelson possessions still in private hands.
Nelson’s watch will be offered at Sotheby’s Treasures sale in London on July 4, alongside other stand-out works such as objects once owned by Marie-Antoinette, Napoleon Bonaparte and Antonio Canova's Bust of Peace. The sale takes place during Sotheby's annual Old Masters Week.