River
The same applies to Fiume, an area that was Austrian territory for centuries, from 1465 to 1779, and subsequently Hungarian until 1848. After Austria and Hungary merged in 1867, Fiume was granted a separate status within the Hungarian part. This lasted until 1918, when Hungary and Austria went their separate ways again. Fiume was the Italian name for the city of Rijeka, currently the principal port city of Croatia. The photo shows the city's main shopping street: the Korzo. In 1918, Fiume was part of the Croatian part of Yugoslavia from October 28 to November 17. However, from November 17 to September 12, 1919, Fiume became an occupied territory of the then-existing Allies. Italy and Serbia, however, continued to dispute control. The area issued its own postage stamps. Prior to that, Hungarian stamps were in use. These stamps can only be identified by the postmark Fiume.
Hungarian stamps were provided with the overprint RIVER without the face value being changed. On January 30, 1919, the first series appeared, printed by Zanardini & Co. in Italian values of centisimi and corona.
The lowest values featured the symbol of liberty as an image: a female figure with a headband topped with a star. Higher values featured an image of the tower of Fiume Town Hall, a harbor view, and the Statue of Liberty.
On May 18, 1919, a series of stamps was issued commemorating the announcement of Fiume's annexation to Italy. The surcharge on each stamp was intended for the formation of a study fund. On December 3, 1919, this series was overprinted with the text: *Valore globale* and the face value. The reverse side of the stamps was printed with a security feature: the words *POSTA DI FUIME* three times.
The stamp issued on September 20, 1919, depicting Dr. Antonio Grossich, President of the National Council of Fiume, was also issued with an overprint on September 12, 1920. The Free City-State of Fiume was proclaimed on September 12, 1919, and on October 10, 1919, three stamps appeared with the overprint FRANCO and the face value.
These overprints were applied by hand, and that is clearly visible. Later, more stamps appeared with that overprint, but this time applied by printing press.
On November 12, 1920, the Treaty of Rapallo was concluded between Italy and the Kingdom of Serbs, Croats and Slovenes. A year earlier, on September 12, 1919, was Gabriele D'Annunzio with his irredentists, he invaded Fiume and formed his own administration. A year later, a series of stamps was issued bearing his portrait. A day earlier, a stamp had been issued exclusively for franking outgoing newspapers. The stamp was designed in the shape of a triangle on its point.
The Treaty of Rapallo formally stipulated that Fiume would become a Free State. The series of stamps featuring an image of D'Annunzio was overprinted with the text: Governo Provvisorio.
The series was issued on February 2, 1921. On April 24, 1921, another series was provided with the overprint Constituente Fiumana and the date 24-IV-1921. This overprinted series was provided with an additional overprint with the year 1922 on March 23, 1922.
In 1924, Fiume became part of the Kingdom of Italy. The Second World War once again brought about a great many changes in geographical and political terms. But during a short period from December 1919 to February 1924 alone, 195 different stamps were issued, in addition to 26 postage due stamps. Who would have been in charge of the stamp issuance policy here?

Nice article about Fiume.
Do you know if there is an association in the Netherlands for collectors of Hungarian stamps?
Yours faithfully,
H. Wolters
Indeed, there is a specialized association in the Netherlands: Filatelist Contact Group East Europe (FCOE). Take a look at their website: http://www.fcoe.nl
I have 2 stamps from Fiume. Are they worth anything, please?
I rather have old stamps for sale
For this too, I must refer to the specialized association: Philatelic Contact Group Eastern Europe.
Or take a look at Stampworld. Do pay attention to the prints!
https://www.stampworld.com/en/stamps/Fiume/