The Byzantine sardonyx bowl and its gold stand – which dates back to the early 19th century – have gone on display at the Edinburgh attraction after it was donated by a famous dynasty of financiers.
The bowl, thought to be worth at least £5 million, can be seen from today at the Hawthornden Court at the museum.
Later it will take pride of place in a brand new European art gallery expected to open at the museum over the next few years.
Curator Godfrey Evans approached the Rothschild family, renowned as avid art collectors, following the death of Major Edmund Leopold de Rothschild three years ago in the belief that he owned the precious “tazza” assembled by the tenth Duke of Hamilton, Alexander, owner of Hamilton Palace.
It had been sold in 1882 by William, the 12th duke, to Alfred de Rothschild, another major banking name in the family, along with five other items for the then huge amount of £24,000, as his family was struggling to make ends meet at the time.
Its treaures were scattered around the world after a sale of the palace’s art collection that year. However, Rothschild had struck a private deal with the duke which saw him end up with the bowl.
Although a legal agreement prevents the museum from disclosing the exact value of the tazza, it is understood that it could fetch up to £5 million if it was auctioned.
However the museum has not had to spend anything. It was allocated its most valuable object under the UK-wide “acceptance in lieu” scheme, which allows people to offer items of cultural and historical importance to the state in full or part payment of their inheritance tax, capital transfer tax or estate duty.
The bowl was bought by the tenth duke while he was British ambassador in Russia in 1807-8. The gold stand which the duke used to transform the bowl into the tazza five years later came up at an auction in London of gold which had been looted from a Spanish royal monastery, at Escorial, near Madrid.
Sir Angus Grossart, chairman of National Museums Scotland, said: “The Hamilton-Rothschild tazza is the single most important acquisition that we have made in many decades.
“Acquiring this wonderful work of art demonstrates our enhanced international ambitions for our collections and underlines our aspirations.
“We have a strategic vision for our future potential and are committed to build upon major acquisitions.”
Culture secretary Fiona Hyslop said: “I’m delighted such an important work of art is now available for the public to see in Scotland.”