The sitter has been identified as the Marchese Giovanni Battista Cattaneo on the basis of the inscription on the letter. This identification appears to be confirmed by the picture's provenance. The painting is first recorded in the Cattaneo family collection in Genoa in the early 19th century. On the assumption that the sitter is Giovanni Battista Cattaneo, this portrait can be dated to Van Dyck's early years in Italy (1621-7), probably to 1625-7 when he was resident in Genoa. It has been suggested that Van Dyck's 'Portrait of a Woman', which came from the same collection in Genoa, was painted as a pendant for this picture. However, the two portraits do not make a convincing pair as both sitters face the same direction.
The National Gallery, Trafalgar Square, London WC2N 5DN