Reverse The edge of the coin features decorative raised denticles. In the central part, an armillary sphere is depicted against a widened cross. Along the arc of the coin's edge, in the spaces between the ends of the cross, are inscriptions in Latin: «SUBQ.», «SIGN.», «NATA», «STAB.», which translates as 'Under this sign he was born and will remain.'
Obverse The edge of the coin features decorative raised denticles. Along the rim: to the right, bottom, and left is a Latin inscription «MARIA. I. E. PETRUS. III. D. G. PORT. REGES. E. BRAS. D.», translating to 'Maria I and Petrus III by the grace of God regents of Portugal and Brazil.' In the central part is the Coat of Arms of Portugal: a heraldic shield crowned with an imperial crown. In the central part of the shield, arranged in the shape of a cross, are 5 small shields each with five bezants. The edges of the large shield feature a wide border with seven castles. The heraldic shield is surmounted by the inscription «17 / 80» — the mint year 1780. At the level of the shield's center, arranged vertically: on the left, the horizontally placed digits «320» between two dots; on the right — two four-petaled flowers between two dots above and below.