1 Centavo Caldas Da Rainha

Caldas da Rainha is a mid-sized Portuguese town best known historically for its thermal spa — but during the acute coin shortage that gripped Portugal in the early 1920s, dozens of municipalities, commercial associations, and even individual businesses issued their own emergency paper cédulas to keep small transactions moving. The Associação Comercial e Industrial was one of hundreds of such bodies that stepped into the vacuum left by the state's failure to supply sufficient bronze and nickel coinage at low denominations.

At 1 centavo, this is about as small a denomination as Portuguese cédulas reach — barely worth anything even at issue, which is precisely why the metal equivalent was so consistently absent from circulation.