5 000 000 000 Mark

Five billion marks, issued by the municipal government of Mainz during the hyperinflationary peak of autumn 1923. German cities, counties, and private firms were legally permitted to issue emergency currency — Notgeld — as the Reichsbank could not print fast enough to meet demand. Mainz was among hundreds of municipalities that exercised this authority, producing notes denominated in figures that would have been incomprehensible two years earlier.

The dry stamp is the sole security measure, applied mechanically after printing. At these denominations, counterfeiting was barely worth the effort — the notes lost purchasing power faster than forgers could work.