500 francs - Principauté de Monaco

Monaco has not issued its own banknotes since the French franc era — the Principality uses the euro and has no independent note-issuing authority. A 2016 paper note denominated in francs with only a watermark as security is almost certainly a fantasy or novelty piece, produced outside any official monetary framework. Gabris is a Slovakia-based designer known for producing privately commissioned "fantasy banknotes" for micronations and non-issuing territories, which is precisely the category this item falls into.