as support by the communists and as treason by most Westerners. Until that time all over Germany food and other necessary supplies had been available only with ration stamps issued by one's municipality. This was the case in East Berlin until the Communist putsch in Berlin's city government in September 1948 – the unitary City Council of Greater Berlin () for East and West. By July 1948 a mere 19,000 West Berliners out of a total of almost 2 million covered their food requirements in East Berlin. Thus, 99% of West Berliners preferred to live on shorter supplies than before the Blockade, to show support for the Western Allies' position. In West Germany rationing of most products ended with the introduction of the Western Deutsche Mark on 21 June 1948. The new currency was also introduced in West Berlin on 24 June and this, at least officially, was the justification for the Soviet Blockade due to which rationing in West Berlin had to continue. However, in the course of the Berlin Air Lift some supplies were increased beyond the pre-Blockade level and therefore rationing of certain goods in West Berlin was stopped. While West Berliners were officially welcome to buy food in East Berlin, the Soviets tried to prevent them from buying other essential supplies, particularly coal and other fuel. For this reason, on 9 November 1948, they opened checkpoints on 70 streets entering West Berlin and closed the others for horse carriages, lorries and cars, later (16 March 1949) the Soviets erected roadblocks on the closed streets. From 15 November 1948, West Berlin ration stamps were no longer accepted in East Berlin. All the same, the Soviets started a campaign with the slogan The smart West Berliner buys at the HO (), the HO being the Soviet zone chain of shops. They also opened so-called "Free Shops" in the Eastern Sector, offering supplies without ration stamps, but denominated at extremely high prices in Eastern Deutsche Marks. Ordinary East and West Berliners could only afford to buy there if they had income in Western Deutsche Mark and bartered the needed Eastern Deutsche Mark on the spontaneous currency markets, which developed in the British sector at the Zoo station. Their demand and supply determined a barter ratio in favour of the Western Deutsche Mark with more than 2 Eastern Deutsche Marks offered for one Western Deutsche Mark. After the Blockade, when