Crowned portuguese arms flanked by value 320 and two flowers, and date.
Obverse script
Latin
Obverse lettering
MARIA·I·ET·PETRUS·III·D·G·PORT·REGES·ET·BRAS·D·
17 79
·320· (Translation: Maria I and Pedro III, by the Grace of God, Regents of Portugal and Lords of Brazil.)
Reverse description
An armillary sphere in front of the Order of Christ cross, without mintmark.
Reverse script
Latin
Reverse lettering
SUBQ.
SIGN. NATA STAB. (Translation: Born under a steady sign.)