New volume in the Frick Diptych series features a contribution by acclaimed figurative painter Nicolas Party paired with an illuminating essay by Frick chief curator Xavier F. Salomon. Little is known about this portrait, painted about 1730. Despite the fragility of the medium--pastel--it is in pristine condition. The portrayal of the man as a pilgrim, with a black cape and holding a staff, may indicate that he was a member of the...