The superb 1992 cleaning of Mantegna's small painting of Saint Mark ca. 1450 in the Städelsches Kunstinstitut in Frankfurt removed any doubts as to its authenticity. The painting, transferred from canvas to wood panel at an unknown point in its history, is examined here as an evocative close-up portrait of Mark, rooted in the icon tradition of Venice, intended to convey a message of particular Venetian import. The four-line penned inscription at the bottom of the painting - now almost fully legible - provides an important due to the message. The inscription incorporates the "Pax 1ibi Marce" phrase of the praedestinatio legend: Christ's promise to Mark, while he was still alive, that Venice would be his ultimate resting place, that he and the city would grow great together. The intimate format and the merging of long-established artistic modes and up-to-date artistic ideas circulating in northern Italy - all of it working in the service of a political message - speak of private patronage in high Venetian political/humanist circles.