A sextant belonging to Captain Arthur Rostron, who came to the aid of the Titanic after it sank, will sell at Henry Aldridge & Son on April 23.
Rostron was the captain of the Carpathia, the first ship to come to the rescue of the stricken Titanic.
He and his crew saved the lives of hundreds of people.
Rostron acquired the sextant in the 1880s, while undertaking his cadet training aboard training ship the HMS Conway.
He used it throughout his career and would certainly have used it to navigate to the site of the wreck.
It's made from brass and is accompanied by its original mahogany presentation box, engraved with Rostron's initials.
The lot is being consigned by his family and is expected to realise around ?�40,000-50,000 ($56,659-70,842).
Auctioneer Andrew Aldridge, told the Scottish Herald: "This is without doubt one of the most important pieces of Titanic memorabilia due to the integral part Sir Arthur played in the rescue of the surviving 705 men, woman and children�Ǫ
"It represents a unique chance for either a museum or collector to bid on an item of this calibre and is a true once-in-a-lifetime opportunity."
A silver loving cup presented to Rostron by "The Unsinkable" Molly Brown realised $198,000 in 2015.
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