In April 1945, just before the collapse of the Third Reich and the end of World War II, Karl Renner (1870-1950) set up a Provisional Government in Vienna. The government consisted of politicians from the Social Democratic Party, the Austrian Peoples' Party and the Communist Party; many of them were returning from exile or Nazi detention, and thus had played no role in the Nazi government.
Renner's government declared Austria to be separate from Germany, and campaigned for Austria to be acknowledged as an independent Republic and the first victim of Nazi Germany. As a result, the Allies treated Austria more as a liberated, rather than a defeated country. Karl Renner meanwhile, was elected as President in December 1945.
To commemorate the first anniversary of the establishment of the Provisional Government, the Austrian post issued a set of 4 perforated stamps on 7th August 1946; the design depicts Karl Renner.
On 5th September, the stamps were issued in imperforated sheets of 8 stamps with a stamp-size label with Arms in the centre; these were printed on yellow Japanese paper. These are the so-called 'Rennerblocks' and are the most expensive and key items of 20th century Austrian philately.