The inkwell was made in 1911, probably to commemorate a new building for the Royal National Mission for Deep Sea Fishermen being opened in the port.
Auctioneer Paul Campbell at Campbells Auctions said he could not reveal who bought it, but added he was "satisfied" the purchaser was to bring it back to Cornwall.
Arts and Crafts style
The inkwell is hallmarked "RTD, Newlyn", known to be the mark of Newlyn-based Reginald T Dick.
It measures 7.5 inches square, 3.25 inches high and is decorated with scenes of fishes and shells.
Mr Campbell continued: "The piece is decorated in an Arts and Crafts-inspired style, which is typical of Newlyn copper, but Newlyn silver is almost unknown.
"I would love to find out why this piece was made and if it was commissioned by the institute or was presented to it."
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