Denmark's National Museum, exercising its right to first dibs, paid one million euros ($1.09 million) for seven of the collection's around 20,000 coins.
"The quality is extraordinary. The collection has become a thing of legend. It's like the princess had been sleeping for 100 years," Helle Horsnaes, head of the National Museum's coin and medallion collection, told AFP.
In 1922, Lars Emil Bruun, a Danish entrepreneur and coin expert, bought the collection from the aristocratic Bille-Brahe family, agreeing to respect the National Museum's pre-emptive right to the collection.
He died the following year, adding in his will a condition to the sale of the collection.
"The story goes that Bruun, after having seen the devastation of the First World War, was very afraid that something would happen to the (museum's) national collection," Horsnaes said.
"And therefore he made a will, saying that his collection should be kept as a reserve for the national collection for 100 years after his death," she added.
Kept hidden away in a secret location for 100 years, a board of trustees handed the collection over to his heirs on November 21, 2023.
It is estimated to be worth $72.5 million.
"People have been talking about it and talking about what will happen now when it is released," Horsnaes said.
"It has taken on a special history of its own."
The seven pieces acquired by the museum date from the end of the 16th and early 17th centuries.
The rest will be sold by the Stack's Bowers auction house in the autumn.
