An exceptionally fine and large narwhal tusk made £30,000 ($47,829) at Charles Miller in London on October 30.
It realised an impressive 50% on its £15,000-20,000 ($23,914-31,886) estimate.
The tusk is mounted on a slate and features a silver plaque bearing the inscription: "PRESENTED TO CORNELIUS FUDGE, MASTER AT ARMS / BY HIS MESSMATES, AS A MARK OF RESPECT & ESTEEM / ON HIS LEAVING HMS 'LONDON' AT ZANZIBAR / TO RETIRE FROM THE SERVICE. SEPTEMBER, 1881".
It is unknown exactly what narwhals use their tusks for, but it is known that only males have them and it is thought that they play a role in determining social hierarchy.
Sunset Over the Royal Naval College, Greenwich, a painting by James Francis Danby, realised £9,000 ($14,348) at the same sale - an increase of 50% on an estimate of £4,000-6,000 ($6,377-9,565).
A well-respected painter of naval scenes, he was the son of Francis Danby - a leading painter of the Bristol School.
His A View of Greenwich from the Thames made $25,000 at an auction in Houston in 2005.
A rare 19th century Dieppe-made model of a paddle steamer realised £8,000 ($12,764).
It features detailed representations of the ship's rigging and fittings.
We have a collection of historical artefacts pertaining to the battle of Trafalgar offered in a limited edition collection - including a piece of wood from the original Victory alongside a piece of Lord Nelson's handkerchief.
Sign up to our free weekly newsletter for more of the latest from the world of collecting direct to your inbox.