20 000 000 Mark Reichsbanknote

By the time this note entered circulation in mid-1923, Germany's hyperinflation had already destroyed any meaningful relationship between printed denominations and purchasing power. Twenty million marks sounds enormous; within weeks of issue it would not buy a loaf of bread. The Reichsbank was printing faster than the economy could denominate, and this note — like dozens of others released that year — was obsolete almost on the day it left the press.

The watermark is the sole security feature, a detail that speaks to how little counterfeiting concerned authorities when the currency itself was collapsing faster than any forger could profit.