Johann, known as Hans, Klinkhoff was the illegitimate child of Emma Kikinis and Max Singer, official supplier of horses to the court. His mother converted from Judaism to Catholicism in 1902 and changed her surname and that of her three children from Kikinis or Singer to Klinkhoff. According to his family, Hans Klinkhoff completed studies at an unnamed technical university and in 1911 founded an engineering office and a commercial agency at Brandstätte 1 in Vienna's 1st district. During the First World War he was stationed with the Austrian navy in Pula. While he was there, he met the painter Ludwig Koch, who was working in the military press office. He had been commissioned to paint a patriotic portrait entitled The Emperor's Thanks, and Klinkhoff stood as a model for one of the figures. Until 1918 he sold reproductions of the picture (large print runs of postcards and prints) throughout the monarchy. Some of the proceeds went to the Gesellschaft vom österreichischen Silbernen Kreuz zur Fürsorge heimkehrender Krieger, an Austrian welfare fund for returning soldiers. After the war, he acquired the painting from Koch for his art collection. Between the wars, Klinkhoff expanded his company and specialized in equipment manufacture, control engineering and thermostats. As the only specialist company of its type in Austria, Klinkhoff-Apparatebau Ges.m.b.H. supplied the necessary measuring and control technology for the Amalienbad, Dianabad and numerous other Viennese swimming baths, as well as the Städtische Hallenschwimmbad in Innsbruck. Klinkhoff acquired a respectable fortune, property and buildings and, according to his son Walter, an impressive art collection, consisting mainly of conservative nineteenth-century art. As a result of the worldwide economic crisis, Klinkhoff's company experienced financial difficulties in the early 1930s. Klinkhoff attempted to rescue the company with the aid of a loan from bank director Hans Zeiszig sen. in return for the recruitment of his son Hans Zeiszig jun. as Prokurist (authorized signatory). Shortly after the annexation, Hans Klinkhoff was arrested for a few days and interrogated by the Gestapo but released again shortly afterwards. In April 1938 he fled with his wife Hermine (née Nass) and their eldest son Fritz to Milan, where his company had a branch office. The second son Walter had already moved to London but returned in early March to Hall in Tyrol for exercises as a reservist in the army. In the first days after the annexation, he managed to leave for Britain. In the meantime, Hans Zeiszig jun. was attempting to Aryanize the company in Vienna. As it was highly indebted, however, the temporary administrator declared it bankrupt in September 1938. Klinkhoff's villas in Vienna and Edlach near Reichenau an der Rax were sold and the proceeds added to the company's financial assets. In 1943 the Städtische Sammlungen Wien (now Wien Museum) purchased the painting The Emperor's Thanks "from assets seized by the Gestapo". Hans Klinkhoff, his wife Hermine and their son Fritz were able to continue from Italy to Switzerland and then to Britain, where they met up with the second son Walter. They were interned there in 1940and shipped to Canada. Hans Klinkhoff's mother Emma was the only member of the family to remain in Vienna, where she took her life on 24 March 1942 at the age of eighty-four, shortly before she was scheduled for deportation.
On 24 March 2009, the Vienna Restitution Commission decided unanimously that the painting The Emperor's Thanks should be restituted to Hans Klinkhoff's legal successors, who generously donated it to the Wien Museum. The whereabouts of the other artworks from the Klinkhoff collection remain unknown.