"Approximately a quarter of an hour after the fire started on Sadovaya, there appeared by the mirrored doors of a currency store on the Smolensky market-place a long citizen in a checkered suit, and with him a big black cat".
The readers of the English Pevear and Volokhonski translation don't know it, but those of most other translations know that the currency store is called Torgsin. It's not clear why Pevear and Volokhonski did not translate the word торгсин (Torgsin) from the original text. Anyway, Torgsin is a typical Soviet contraction of Торговля с иностранцами (torgovlia s inostrantsami) or Trade with foreigners. This was the name for these stores in the '20s and '30s. In theory, anyone with hard currency and valuables could enter this store and purchase unobtainable goods such as food and clothing. There were, of course, security guards at the door who would not let people in if they looked as if they did not possess any valuables.
The Torgsin store was different from the beriozka of the late Soviet period in that the beriozka would only admit foreigners. The purpose of the Torgsins was to collect as much foreign currency as possible by offering quality goods to the employees of foreign representations, tourists and engineers cooperating in projects aimed to realise Stalin's first Five Year Plans. Because the planned objectives were not achieved, the money galore that was expected from the export of grain did not come, so something had to be organised within the country to bring in foreign currency. One of the vehicles - next to the prohibition to possess currency, and consequently the confiscation of it - was the Torgsin system.
Often, Soviets waited near the stores and offered to buy some of the 'exotic' purchases made by the foreigners as they left the store.
The specific store mentioned in the novel is on Smolenskaya Square, at the corner of Arbat and the Garden Ring, and it still functions as a large supermarket today, as a part of the Gastronom chain. My spouse works in the building just next to it, so we can have really every day the nicest baguettes, more French than in France!
Metro: Смоленская (Smolenskaya)