Otto Marx (1897-1974), herd-tester, was born on 3 August 1897 at Hamburg, Germany, son of Carl Marx, businessman, and his wife Lina, ne Steinwehr. Otto was of part-Jewish descent. He fought (from 1914) as a sergeant with the German Army and won the Iron Cross before being made a prisoner of war. Released in 1920, he returned to Hamburg. On 5 July 1923 he married Minna Mollnitz-Schier. While working as a merchant banker with a coffee importing company, he realized the imminent danger facing Jews in Nazi Germany. Leaving his Aryan wife behind, he managed to escape to England in August 1939. He was interned in 1940 and shipped to Australia as an enemy alien in the Dunera which reached Sydney on 6 September that year.
Sent to internment camps at Hay, New South Wales, and Tatura, Victoria, Marx was released as a refugee alien with other 'Dunera boys' to supplement the wartime labour shortage. He joined the Militia on 25 April 1942, served with the 8th Employment Company and was discharged on medical grounds on 20 December 1943. Through a Quaker connexion, Marx was hired as a herd-tester by the co-operative at Maffra. With little knowledge of the dairy industry, he was required to visit farms and stay overnight for the evening and morning milkinga potentially difficult situation for a German in 1944. The milk samples he collected were tested to monitor individual cows' production and butter fat content. He soon procured a caravan which also served as a mobile office. On 3 November 1945 he was naturalized.