This is a sketch by Sir Edwin Landseer of a “Setter Dog.” It dates to 1820.
Compare this dog with Breeze, a retriever that was around in the 1840’s.
The little secret about golden retrievers is that yellow and red retrievers have been around ever since St. John’s water dogs were bred to setters. The fact that the 1st Baron Tweedmouth capitalized upon the color variant to found his line does not mean that the animals weren’t always around.
Of course, most of these dogs would have been “bucketed” before they ever reached maturity.
The reds/yellows were hardly a “secret”. They just weren’t fashionable.
Same as in Flat-Coats and Newfoundlands today.