One of the best-kept secrets of the Cold War was hidden in an unassuming residential area in Cochem on the Moselle River. It was said that even the otherwise well-informed East German Stasi did not know that beneath a training and recreation facility operated by the German Bundesbank, specially designed banknotes were stored for use in times of crisis or war.

Those embarking on a guided tour of the Bundesbank bunker in Cochem experience a journey back in time to a facility up to 30 meters deep and 1,500 square meters in size, nestled into the Moselle hillside. For decades, the bunker meticulously housed packaged notes of the so-called replacement series, totaling nearly 14.5 billion Deutsche Marks. Additionally, almost 11 billion Deutsche Marks were stored at the Bundesbank in Frankfurt.

Fearing that the Warsaw Pact could inundate Germany with counterfeit money, thereby driving inflation and undermining confidence in currency and the economy, plans for a highly secretive replacement series took shape in 1959. This replacement series, known as BBK II, was produced from 1963 to 1974. It was not intended to introduce a new currency. Instead, the existing banknotes – with over 25 billion Deutsche Marks in circulation in 1963 – would have been exchanged with the Deutsche Mark replacement series.

If it had come to pass, everything would have had to happen quickly: citizens would have had only 14 days until the existing banknotes lost their validity. Through press, radio, and television, they would have been urged to exchange their banknotes at banks and savings banks. Replacement notes would have been transported from Cochem and Frankfurt to the regional central banks and further distributed to financial institutions within their jurisdictions.

The notes in the replacement series closely resembled the originals on the front, but the back was entirely different. The one hundred Deutsche Mark note, for instance, featured the cosmographer Sebastian Münster in both the circulation and replacement series, although there were differences in detail. On the back, however, the replacement series featured not the Federal Eagle but a graphic pattern.

In the Cochem bunker, a total of 18,354 boxes were stacked up to the ceiling, each filled with 20,000 notes, in denominations of 10, 20, 50, or 100 marks. 5- and 500-mark notes were not included in the emergency variant.

The construction of the bunker complex commenced in 1962 and included blasting operations in the slate rock. Residents were told that shelters were being created for the Bundesbank's training and recreation facility. During the Cold War, bunker construction under public institutions was common practice. Starting in 1966, money was delivered to the bunker at irregular intervals. Only a select few were aware that beneath the educational and recreational facility in Cochem, there were billions in assets reserved for emergencies. Among them were reportedly the Bundesbank's directorate and some auditors from the headquarters in Frankfurt, who irregularly came to check the money.

In case of emergency, up to 80 Bundesbank employees would have worked in the bunker. For them, there were extremely spartan work and sleeping rooms. With only 36 beds available, they would have had to sleep in shifts. There was also a doctor's room, a kitchen, a washroom, and a men's toilet. What was not considered in the construction planning was a women's toilet.

Fortunately, the emergency never occurred, so the facility served solely for the storage of banknotes. In 1988, even before the fall of the Berlin Wall, the destruction of the replacement series was decided. By early 1989, the banknotes were removed, shredded, and burned.