Chief Vatican restorer Maurizio De Luca said Thursday that the face of a man on horseback in the artist's "The Crucifixion of St. Peter" could well be the artist, though he told AP Television News that nobody will ever know "with absolute certainty that the face is Michelangelo's."
The Vatican announced earlier this week that the restoration had been completed after five years at a cost of euro3.2 million ($4.5 million).
The frescoes were commissioned by Pope Paul III and painted between 1542 and 1549, when Michelangelo was 75. They were his last works.
The chapel, generally known by its Italian name Cappella Paolina, is used by the pope and is not open to the general public. It contains two Michelangelo frescoes, the other of which depicts the conversion of St. Paul.
Pope Benedict XVI will inaugurate the restored chapel with a prayer service Saturday.
De Luca praised the precision of Michelangelo's work on the fresco, particularly since it is far above the ground.
"The details of it have been painted with the tip of the brush, almost a minute attempt to achieve precise details, which was unneeded given the distance between the fresco on the ceiling and the people looking at it," De Luca said.