5 000 000 000 Mark

Siegkreis was one of dozens of German administrative districts forced into emergency currency during the hyperinflation of autumn 1923, when the Reichsmark was losing value faster than the Reichsbank could supply physical notes. A five-billion-mark denomination sounds grotesque, but by October 1923 it represented only a few days' purchasing power at best — the exchange rate against the dollar was deteriorating by the hour.

Rhenania-Druckerei in Bonn was a regional commercial printer, not a specialist security firm, and the official stamp was the primary — arguably the only meaningful — authentication device keeping counterfeits out.