The Maestro di Barga
Madonna Enthroned with Angels and Saints: Detail, Left panel with Saints Abundius and John the Baptist
Tempera and gold on wood panel
Pinacoteca Vaticana, Rome
St. John's has the usual long cross and the usual tunic of camel-skin under his red and blue mantle. His scroll has most of the phrase Ecce agnus dei, ecce qui tollit peccata mundi, "Behold the lamb of God, behold him who takes away the sins of the world."
The Italian inscription below identifies the other saint as sancto aconcio, a variant of "St. Abundius." This saint was a sacristan at St. Peter's, Rome, in the 6th century. According to Gregory the Great, a woman severely weakened by palsy crawled to him on her hands and knees and said St. Peter had sent her to be cured by him. He reached down, pulled her up, and she was fine (Dialogues, III, 25).
A sacristan is a lay person and would not wear the liturgical dalmatic A wide-sleeved, long, loose vestment open at the sides, worn by deacons and bishops, and by some monarchs at their coronation – Google Definitions and alb A linen vestment with narrow sleeves, worn chiefly by priests, now invariably white in the Western Church but can be in a color in the Eastern Church – Dictionary.com shown here because they are liturgical vestments. Nor would he be tonsured. But it was possible to move into the clergy after starting as a sacristan, as the biship Paulinus of Nola had done in the fourth century (G. T. Ryan, 8).
The Roman Martyrology lists St. Abundius for April 14. In other documents his name has been garbled through the years to "Acontius," "Agoncius," and so on.
This image in full resolution
More of St. John the Baptist
Photographed at the Pinacoteca Vaticana by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.