This, from the website of The Gordon Setter Association of England....
Although it is often credited that the Gordon Setter was the result of the Duke of Gordon crossing his black and tan Scottish collies with his Setters, to quote from the definitive work on the breed - The Gordon Setter - History and Character by G St. G M Gompertz - published by the author in 1976:
“There are reliable records to show that the Black and Tan Setter was in existence as a separate breed long before it was taken up by the Duke of Gordon.”
In the first half of the 18th Century records show that there were several noted kennels of Black and Tan Setters in the Midland Counties well before the Duke took up the breed in the early part of the 19th Century - obtaining his original stock from Thomas William Coke, late to become the Earl of Leicester, and that some of this stock was maintained as pure-bred stock, without the introduction of outside crosses for many years. It seems to be clear that this was the reason that the Kennel Club, founded in 1873, classified the breed at this time as “The Black and Tan Setter.”
Some 50 years were to elapse before in the Kennel Club Gazette of 1924, it was announced:
“In the list of breeds ... dated 1st January 1924 ... [without any reason being given] ... the Setter (Black and Tan) ... is now officially designated ... “The Gordon Setter.”
... possibly in recognition that by this time most Gordon Setters, but not all, could be traced back to the Gordon Castle strain, whilst it would be wrong to accredit solely the production of the breed to the Dukes of Gordon there is very little doubt that they played a very important part in the breed's development.
The effect that Robert Chapman from the late 1870s to the end of the century, and Isaac Sharpe from that point to just before 2nd World War, exercised cannot be ignored. They possibly exerted a greater influence in the refinement and uniformity of the breed and produced a type better suited to changing needs.
Within this brief précis it is impossible to examine and come to a definitive conclusion on importance of the individual contributions made to the development of the breed.
Just more evidence exploiting the facts of what an extremely eclectic breed our Black and Tan setter is...
We'll never really know what went into the mix, but, if we observe our dogs closely on a regular besis, we can see traits that could be attributable to other breeds..
Long Live the Gordon, ever changing even to this day!