What specific role do the carvings above the donor's head in the present work, analogous to those in van Eyck's earlier van der Paele and Madonna of Chancellor Rolin, likely serve?
A landscape can be seen through the window behind St. Catherine. Because of the miniature scale of the painting it can be seen only at close up. The view is built with extremely fine brushwork and shows a number of highly detailed buildings and hills before snowcapped mountains.A lance rests against the shoulder of a youthful-looking St. Michael. Michael is dressed in elaborately jewelled and coloured armour, his left arm holding his helmet, while his right hand rests on the shoulder of the donor as he is presented to Mary. The donor kneels in prayer before the Virgin, with his hands held upwards as if in prayer, although they are not clasped. He wears a gold ring on his right small finger, and is dressed in a long olive-green houppelande, at the time the height of fashion and an indicator of status within the Burgundian court. The gown has a fur-lined high collar and deep baggy sleeves, also lined with fur.  The donor's bowl-shaped haircut, rounded at the fringe but cut above his ears, is also typical of mid-1430s Netherlandish fashion. Except for the red hood, the garment closely resembles that worn by the groom in the Arnolfini Portrait.The capital of the pillar above the donor's head is lined with carvings of military scenes. Similar carvings are seen near the donor in van Eyck's earlier van der Paele and Madonna of Chancellor Rolin, and where they depict events or personal circumstances from the donor's life. Those in the present work likely serve a similar role, however because the donor is unidentified it is unknown as to what they may refer. Elisabeth Dhanens speculates that they might depict the sarcophagus of Hippolytus in Pisa, which she believes adds credibility to the belief the donor was of Italian origin; she also notes the military scene reflects St. Michael's status as military commander. Ward compares the carving to a similar one found in the Washington Annunciation. Unlike in van Eyck's earlier votive portraits the donor is positioned at a remove from the Marian apparition, and at a much smaller scale to Mary on a triptych wing.The lettering running along the edges of the panel's frame consists of a prayer fragment from the liturgy for the feast of St. Michael. The extract reads HIC EST ARCHANGELUS PRINCEPS MILITAE ANGELORUM CUIUS HONOR PRAESTAT BENEFICIA POPULORUM ET ORATARIO PERDUCIT AD REGNA COELORUM. HIC ANGELUS MICHAEL DEI NUNTIUS DE ANIMABUS JUSTIS. GRATIA DEI ILLE VICTOR IN COELIS RESEDIT. A PACIBUS ("This is Michael the Archangel, leader of the angelic hosts, whose privilege it is to grant favours to the people, and whose prayer leads them to the Kingdom of Heaven. The Archangel Michael is God's messenger for the souls of the just. By the grace of God, that great victor has taken his place in Heaven, on the side of peace'").
they depict events or personal circumstances from the donor's life