2 000 000 000 Mark

Berchtesgaden's two-billion-mark notgeld dates from the hyperinflation peak of late 1923, when German municipal and district authorities were legally permitted — effectively compelled — to issue their own emergency currency to meet payroll and local commerce. The Reichsbank simply could not print and distribute fast enough. By November 1923, when the Rentenmark stabilization finally cut off the spiral, denominations of this magnitude had become routine in daily transactions rather than remarkable.

The watermark security feature is worth noting: at this tier of local emergency issue, such precautions were more administrative habit than practical anti-counterfeiting measure — nobody was going to forge a note worth fractions of a cent in real terms.