This is another instance of Dan Beard, in his illustrations, creating additional meanings for the story MT has Hank tell in his words. All MT's contemporary readers would immediately have recognized that this slave driver looks exactly like financier Jay Gould, one of the notorious robber barons from the period. Whether they would also have recognized the driver's victim as in any way emblematic of the millions of blacks who were enslaved before the Civil War was, I think, much less likely.
The Barrett Collection, UVA PS1308 .A1 1889