The Somali Rupia was introduced between 1909 and 1910. First, bronze coins denominated in Besa were introduced, followed by silver coins denominated in Rupia in 1910. The Rupia replaced several currencies, including the Maria Theresa thaler and the Indian rupee, to which it was equal. The Rupia was replaced by the Italian Somaliland lira during a transition period between July 1, 1925, and June 30, 1926,[1] at a rate of 8 lire = 1 rupia.
V. Filonardi & C. looks like a private issue but in reality it was sponsored by the Italian government to assist the company in overseeing the interests of Italy in the region. This made the company de facto government in this area.
We thus have two different stories. The Wikipedia article references the Banknote Book. Does anyone have a copy of this to check exactly what's said? On its own, being a promissary note doesn't make something Exonumia (otherwise all Bank of England notes would be there). Similarly, if the notes were meant to circulate with the existing coinage rather than replace them, that would be the normal situation for a banknote.
Former Numista referee for banknotes from Ireland, Northern Ireland, Scotland, Wales and Saint Helena.