Fredrik Vilhelm, Elector of Brandenburg (1620–1688).
Canvas 125 x 103 cm
Björnsnäs herrgård, Östergötland, Sverige.
Svenska Slott och Herresäten, Ny följd, ed. Albin Roosval, Östergötland, 1920, ill. at p. 25 (in the salon).
Compare the motif to Sir Anthony van Dyck portraits depicting for example Sir Edmund Verney. The gentleman is wearing armor and is slightly turned with the right side closest to the viewer. Right hand is resting on a helmet and he holds a baton of office in the left hand.
Literature: Susan J Barnes "Van Dyck, A complete Catalogue of the Paintings", compare ill. at p. 608.