The medallion is inscribed in Latin: “The maiden Sofonisba Anguissola, depicted by her own hand, from a mirror, at Cremona.”
Sofonisba Anguissola was an artist who came from a noble family in Cremona (northern Italy). She is well known for the paintings she made of herself and her family (she was the oldest of seven children). In 1559, she became a lady-in-waiting to the Queen of Spain, Elisabeth de Valois, and continued to produce works while at the court of King Philip II until 1573. Interestingly, Sofonisba painted at least 12 self-portraits at a time when this was not a particularly common subject for artists (in the next century, Rembrandt would be the first artist to make the self-portrait a major part of his oeuvre).
Women in Renaissance Italy were generally barred from becoming apprentices to master artists (the standard way in which artists were trained during the Renaissance). Female artists tended to come from families where a father (or sometimes a brother) was an artist. In this way they could receive training and bypass the apprenticeship system. Sofonisba is atypical in this respect—her father was not an artist. Instead, she studied with other artists—with Bernardino Campi as well as Bernardino Gatti (Il Sojaro)—who exposed Anguissola to the fundamentals of painting, such as the importance of disegno (drawing or design).
We have a letter from the artist’s father dated 7 May 1557 thanking the great Italian Renaissance painter, sculptor, and architect, Michelangelo, for the “honourable and thoughtful affection that you have shown to Sofonisba, my daughter, to whom you introduced to practice the most honourable art of painting.” While it is clear from this note that Sofonisba met the famous Renaissance artist, it has also been suggested that she may have even studied with Michelangelo. Certainly the renown she gained in Italy helped to secure her position as lady-in-waiting at the Spanish court.
(https://smarthistory.org/sofonisba-anguissola/)