It is fascinating to see how a single image can capture the collective imagination and sustainably resist any attempt at a logical explanation.
What experts really think of this image
Experts in historical photography, on the other hand, take a much more measured stance. There are several simple and perfectly plausible explanations: the man is looking at his watch, adjusting something to his ear, or holding a pipe near his face. A completely ordinary gesture, captured from a particularly deceptive angle.