A Winslow Homer mystery

My father saved all kinds of clippings, signed posters and prints by artists he admired; most things of value were sold before his death in 1967. 
Among the photos from his studio, recovered in 2009, was a black and white 8x10" image of a boy. It's kind of academic-looking, and I thought it was either by another artist or a charcoal drawing by Jim while he was a student. 
Two days ago I visited The Clark Art Institute in Williamstown, Mass., a gorgeous museum. Very strong permanent collection (Monet, Manet, Renoir, Degas, Sargent and Homer, among many others) and "Van Gogh and Nature," up through September 13.
Turning a corner in the permanent collection rooms, I found myself staring at the original of Jim's photo of the boy. Another wonderful shock of recognition in my quest to understand Jim's artistic life! 
Interestingly, the picture--a commissioned portrait of young Charles Prentice Howland, by Winslow Homer (1878)--had never been publicly shown until The Clark acquired it in 2014. 
So how did Jim happen to see it? And the photo, which seems to have been professionally taken?
Here's the photo Jim had. Guess I can take it off the list of Jim's still-sought artworks!