The stamp in right side reproduces a painting of the eighteenth century Portuguese painter Vieira Lusitano (1699 - 1783), Royal Painter to King John V of Portugal.
This issue celebrates the centennial 8 of the birth of St. Anthony of Lisbon or St. Anthony of Padua (Lisbon, Portugal, 1195 - Padova, Italy, 1231). He is the patron saint of Lisbon and is venerated with equal devotion, both in Italy as in Portugal.
Thank you very much, Lorenzo!