The thousands of often desperately poor Jewish refugees in Japan had been kept from destitution by a currency arbitrage. Japanese citizens were forbidden from owning any foreign currency, and in consequence a black market existed, particularly in dollars. … The Jewish Labor Committee would open bank accounts for refugees in Japan such as Melamed's family, and deposit yen in them. When refugees received a U.S. visa, they would take the visa to the bank, and they were then allowed to convert the yen in their account to dollars at the official rate. They would take these dollars on board the ship taking them from Japan (Melamed still remembers the "little briefcase" in which his father did this) and register them with the ship's purser to prove they were not penniless. After doing so, they would then return the dollars to a representative of the Labor Committee, who would take them back onshore and convert them back to yen at the much more favorable black-market rate (Melamed interview).

Donald MacKenzie, An Engine, Not a Camera, loc. 642