10 000 000 000 Mark Fleckenssparkasse

The Fleckenssparkasse Horneburg was the savings institution of a Flecken — a German municipal designation sitting legally between a village and a full town — and this note belongs to the notgeld emergency currency wave of late 1923, when hyperinflation had rendered Reichsbank denominations functionally useless almost as fast as they could be printed. Local authorities, savings banks, and even private firms across Germany issued their own paper to keep commerce moving. A ten-billion mark denomination from a rural Lower Saxon savings institution is exactly the kind of piece that was spent within days of issue, often within hours.

Horneburg's population at the time was well under two thousand. The denomination reflects mid-October 1923 purchasing power — by November, it would have been nearly worthless again.