10 Kronen (CF stamp)

After the dissolution of Austria-Hungary, Fiume's status became the subject of one of the ugliest territorial disputes of the post-WWI settlement. Italy claimed it, Yugoslavia claimed it, and for a brief period in 1919–1920 the city was seized by Gabriele D'Annunzio's irregular forces, who declared the Italian Regency of Carnaro. The Città di Fiume — the municipal government, not D'Annunzio's short-lived state — stamped existing Austro-Hungarian Kronen notes with a "CF" overprint to establish local monetary authority during the interregnum.

Forgeries of the CF overprint exist and are well-documented. The genuine stamp shows consistent ink density and crisp letterform edges; blurred or offset impressions warrant scrutiny before attribution.