Released into circulation: 24 June 1997
Metal composition: the core of the coin is made of an alloy consisting of 92% copper, 6% aluminium and 2% nickel, while the ring is made of an alloy exhibiting a silver lustre, which consists of 75% copper and 25% nickel.
Diameter and weight: the coin is shaped as a regular dodecagon, with the circumscribed circle diameter of 32 mm, and weighs 12.75g. The core of the coin is 18mm in diameter and weighs 4.05g. The ring is 18mm in inner diameter and weighs 8.70 g.
Motif on the obverse: the central part of the coin's core carries the symbol of the Congress, an elliptic circle within which eight elongated rhombs are placed in two vertical columns, pointing at one another with their tips. Of the five rhombs in the left column, the third and the fifth are filled with vertical lines. The right column contains three rhombs, all filled with vertical lines, symbolizing the red and white fields of the Croatian historical coat of arms. All eight rhombs are connected, forming the capital letter "E" (i.e. Esperanto). An identical rhomb is placed centrally at the lower part of the ring, with the inscription "UNUA KONGRESO DE KROATAJ ESPERANTISTOJ" beginning on the left side of the rhomb and stretching along the ring to the its right side. The second, inner, strip of the ring's surface features the inscription "PRVI KONGRES HRVATSKIH ESPERANTISTA", separated by the minting year, "1997", placed centrally in the lower part of the strip, above the elongated rhomb.
Motif on the reverse: the central part of the coin core features the denomination numeral "25". The outlines of the number "25" reveal an image of a marten turned to the right, with the marten's body integrated with the denomination numeral. Positioned centrally at the lower part of the coin ring is the coat of arms of the Republic of Croatia, bordered at the left by a blooming laurel branch and at the right by a common oak branch with acorns. The upper part of the ring bears the inscription "REPUBLIKA HRVATSKA".
Occasion commemorated: holding of the first Croatian Esperanto Congress, in Zagreb, on 31 May and 1 June 1997
Items issued: 300,000