20 000 000 Mark Kreis Mayen

Kreis Mayen, an administrative district in the Rhineland, issued emergency currency throughout the hyperinflation crisis of 1923 as the Reichsbank's own notes became worthless faster than they could be printed. By the time denominations in the tens of millions became necessary — mid-1923 — local authorities across Germany were effectively running parallel monetary systems out of sheer necessity, with no central coordination and wildly inconsistent overprint practices.

The Rhineland's occupation by French and Belgian forces after 1923 added a further complication: some district-issued notes circulated in a zone where German monetary law was actively contested.