1 Reichsmark, Reichskreditkassen

A Reichskreditkassenschein — occupation currency, issued by the German military administration in territories the Wehrmacht held and legal tender only there.

The mechanism was extraction. German forces were paid in these, spent them locally, and the occupied country's central bank was obliged to redeem them — so the occupation financed itself out of the occupied economy. They were used across Poland, France, the Low Countries, the Balkans and the occupied Soviet territories.