20 Heller Hinterbrühl

Hinterbrühl is a small village south of Vienna, best known for being the site of the underground Heinkel aircraft factory built inside the Seegrotte caves using concentration camp labor — but this note predates all of that by two decades. Austrian municipal notgeld of this type was issued in response to the severe coin shortage that followed the First World War, with hundreds of small communities printing their own fractional notes between 1919 and 1921.

The official stamp serves as the sole security measure — entirely typical for village-level issues, where the local seal and the inherent obscurity of the issuer were considered deterrent enough against forgery.