Bruun collected coins from an early age, and with his increasing wealth his collection developed into one of the largest private collections of its time of Danish, Norwegian, Swedish and British coins and medals. In 1914 and 1918, he sold the Swedish part of his collection. In 1922, shortly before his death, he acquired an extensive coin collection which had belonged to the counts of Brahesminde. The British part of his collection was sold in auction in London after his death, except for the coins from
Northumberland,
East Anglia and
Ireland, which were donated to the Royal Danish Coin and Medal Collection at the
National Museum of Denmark. It was initially deposited at the Museum of National History at
Frederiksborg Castle, but was transferred to Nationalbanken (the central bank of Denmark) in Copenhagen. On 17 September 2024, the first batch of coins, in 286 lots, was sold at auction for 14.82 million euros ($16.5 million). ==References==