The sword-like tusk of a whale known as the ''unicorn of the ocean'' will take pride of place at the new Lee Kong Chian Natural History Museum when it opens next year.
The narwhal tusk, which is at least 200 years old, had belonged to businessman ''Whampoa'' Hoo Ah Kay, one of Singapore's pioneers of the 1800s.
On Wednesday, his greatgranddaughter Hoo Miew Oon, 79, donated the family heirloom to the museum, formerly known as the Raffles Museum of Biodiversity Research.
The 2.7m-long tusk, which when placed upright is as tall as the tallest human in history, had been given to Whampoa in the 1860s by the Russian government, for whom he was consul in Singapore.
It then remained in his family for four generations. It is considered a rare specimen, as these tusks grow only as long as 3m.
''I will miss it,'' Madam Hoo said at her Dempsey home, as professional movers engaged by the museum packed the spirally tusk.
But she insisted this was the right time to give it up. ''The museum holds more than 500,000 specimens. I know it will be in its good hands.''
The artefact is her ''treasured birthday gift'' to the nation for its 50th year of independence next year, she added, happy that the public will finally be able to see it.
The narwhal tusk is actually an extremely long tooth of the male of the species. The mammals have other teeth that usually remain much shorter. While scientists are uncertain of the tusk's exact purpose, they believe it to be used for mating rituals, and for males to fight off rival suitors.
Narwhals are considered a moderately threatened species, with an estimated 75,000 still alive in waters around the Arctic circle.
The Inuit people in northern Canada and Greenland have hunted them for their tusks and skin for more than a thousand years.
The museum's project manager, Dr Tan Swee Hee, called the donation ''unprecedented'', and said it takes on added importance because of its provenance. ''We have never had anything so spectacular donated to us.''
The tusk - believed to be the only one here - will be on permanent display in the museum's mammal zone.
It was first kept at Whampoa Gardens, where Whampoa displayed his rare animal and bird species, then in the Club Street home of his son Hoo Keng Tuck, Madam Hoo's late grandfather.
During World War II, it escaped the notice of Japanese soldiers as her grandfather, a lawyer, hid it behind a giant four-poster bed covered with mosquito netting.
The museum has received other prominent donations in the past, including from Whampoa.
In 1877, three years before he died, he gave the then Raffles Museum a tooth from a stegodon, a prehistoric animal similar to elephants and mammoths.
The museum also has in its collection the skins of gibbons, orang utans and sun bears. They were donated by animal trader William Lawrence Soma Basapa, who set up the now long-gone Punggol Zoo in 1928.