Police said they are on the lookout for criminals swindling cash from people with a scam involving old German currency notes and bonds that are now worthless.
In late November, police cracked down on a group that defrauded a man of cash by convincing him to buy a color copy of a 1 billion German mark note that is no longer in circulation, the sources said.
The group said the note was a mark bond and that the German government would redeem it for 10 million yen, they said.
The old German currency notes were printed and circulated in the Weimar Republic (1918-1933), during which the country suffered hyperinflation in around 1922-1923, German diplomats stationed in Tokyo said.
At that time, a 1 billion mark note would buy just one egg.
The German Embassy in Tokyo said it has received more than 10 inquiries this year on how to convert the worthless currency notes and foreign currency-denominated bonds into cash.
Bonds denominated in foreign currencies were swiftly moved out of the country during the turmoil that followed the end of World War II. Bonds of this type can no longer be converted into cash, the diplomats said.
Nikolai Putscher, a senior official at the German Embassy, expressed regret regarding the occurrence of fraud cases involving old German currency notes and bonds.
He also asked people in Japan to contact the embassy if they have anything suspicious to report in connection with the case.