Hans Peter Kraus also known as H. P. Kraus or HPK. 12 October 1907-1 November 1988.
Austrian born book dealer, who settled in the United States at the outbreak of WWII. He was described as being the most successful rare book dealer  in the second half of the 20th century. Kraus specialized in medieval illuminated manuscripts, incunables (books printed before 1501: Wikipedia page ), and rare books of the 16th and 17th centuries, but would purchase and sell almost any book that came his way that was rare, valuable and important.
Purchased the Voynich Manuscript from Anne Nill in 1961 for $24,500, and after seven years of unsuccessfully attempting to sell it for as much as $160,000 donated it to Yale University in 1969, where it now resides in the Beinecke Rare Book and Manuscript Library. (He also donated a number of other books and manuscripts to the Library of Congress etc at various points.) The VM is mentioned in Catalogue 100. (Various of his catalogues come up for sale in book/ephemera fairs and other places.)