My assessment of this piece by George Horlor is the red dog and black and tan dog represent are most likely Gordon setters. The other dog is a prototype of what became the English setter.
These dogs are more heavily-built setters than we typically imagine them today, even when we consider that Gordon setters are bigger and more heavily built than the other breeds.
These dogs definitely had a role in the development of the retrievers. The red dog has some features we ‘d associate with modern golden retrievers . The skull is broader, and the build has some bone to it.
Also note the lighter, almost golden shadings on the red dog. These features are very strongly associated with very dark golden retrievers.
So when we think of setters from the eighteenth and nineteenth centuries, we should not automatically assume that all of them were like the dogs of today.
Some of the dogs were indeed much more retriever-like than we might have previously assume.
And the connections between setters and the “setter-retrievers” (goldens and flat-coats) become more obvious.