The story
From 1921 until 1927 during the New Economic Policy trading of foreign currency in Soviet Union was legal. In 1927 however it became illegal to possess and trade foreign currencies (unless specified by the law otherwise) with a punishment up to six month of imprisonment. Businessmen that were often referred as NEPmen during this period of time were banned from using it in everyday commerce. As result of this policy it became necessary to have places where goods could be purchased for foreign currency. The money were usually spent by workers who earned abroad or by tourists and westerners who visited the Soviet Union.
From Wikipedia’s article on Beryozka (Russian retail store), shared under CC BY-SA 4.0.3
