This painting belongs to a limited corpus of works made using the "verre églomisé" technique. This gold leaf engraving technique faintly recalls the gilded glass of antiquity. Revived in Italy during the 13th century, painters in the northern part of the peninsula highly appreciated it for its exquisite character and the refinement of its details. The work has been attributed to Jacopo di Cione, a painter from the prestigious lineage of the painter Giotto.
The depiction of the young girl with the unicorn above the Virgin highlights the chastity and virginity of the mother of Christ. According to mediaeval texts, only a virgin girl could go near the mythical animal.