Reverse: On top along the rim, “MORSWIN” for Porpoise. In the center, an image of two harbour porpoises, and a portion of the map of Poland showing the north coast and the Baltic Sea. At the bottom, “Phocoena phocoena”, the harbour porpoise’s scientific name.

Obverse: On top, "RZECZPOSPOLITA POLSKAA" for Republic of Poland. In the center, an image of the eagle, the state emblem of the Republic of Poland, the year of issue, and the images of Poland’s national flag on each side. Under the Eagle’s left foot, the Mint mark. At the bottom, the face value.

Harbour porpoises are one of the world's smallest cetaceans, growing to an average length of 1.55 meters and a mass of 55 kilograms. Like dolphins, killer whales, and sperm whales, harbour porpoises belong to the toothed whales suborder (Odontoceti).