It's a side compartment from an altarpiece with the figure of Saint Vincent. The Saint, dressed as a deacon, appears kneeling in a mountain landscape. He's resting his right hand, with which he's holding the palm of martyrdom, in the windmill's wheel in which his body was tied up before he was thrown at the sea to be eaten by fish. With his other hand he's holding an open book in which you can read fragments of an antiphon and a psalm.