Captain Ernst Malmberg (1867-1960) was a prominent member of the cultural "elite" in the early 20th century. It would seem that there was no Swedish writer or painter of any significance who did not regularly visit the Malmberg home. Ernst Malmberg was also a collector of manuscripts. Somewhere around 1940 he apparently fell on hard times and a significant amount of his collection ended up with a scrap dealer in Uppsala, where it was acquired by the university library. It turned out to be material from Riga, documents from the Swedish administration of Livonia.
Where and how had Malmberg obtained these records? Well, subsequent events would suggest that he claimed to have bought them in Berlin. It's an odd collection - many small receipts or notes of no significant content besides a signature, which suggests that the person who had removed them from Riga was more interested in autographs than in the content. However, there are exceptions such as a letter by Field Marshal Johan Banér about the battle of Wittstock in 1636 or financial records from the period of the Polish-Swedish-Russian War of the late 1650's. Many of the letters are from the period of the Great Northern War and they appear to have been unknown to the Swedish military historian Hugo Uddgren, who first came to Riga in 1909 as well as to the Estonian historian Henrik Sepp, who in 1930 published a book about the siege of Narva in 1700.
Another collector worth mentioning in this context was the historian Carl Schirren (1826-1910), who not only had built a large collection of copies from various European archives but also possessed a significant amount of original documents. Apparently he had in the 1860's and 1870's been allowed to remove items from the archive of the Swedish Governor General of Livonia, records which after his death eventually ended up in the Swedish National Archives. Given Schirren's standing as en expert on the Great Northern War his collection of originals is undoubtedly more well-known than Malmberg's, but the latter could very well be just as important.