In 1997, Kroatia had it's first Esperanto Congress.
To commemorate that not a set of stamps were issued, but a real coin.
Quite special, since the coin had also a nice face value of 25 Kuna, and was emitted as a bimetallic coin.
Above that, the coin is special in another way.
So far it's the only dodecagonal coin i have (seen).
It's truly a beautiful coin, and one of the special items in my collection.
I wasn't in Kroatia that time, and was lucky i could buy the coin years later over Internet.