Pre-Renaissance
Since the early 20th century, an anonymous master in this period is someone known not by their name but by the name the subject and/or commissioner of their best-known work. For example, the Master of the Bardi St Francis is the painter commissioned by the Bardi family to paint their chapel at Basilica di Santa Croce in Florence, and who painted (among other paintings) that of the Life of St Francis there.
Read more about this topic: Anonymous Artists