This model was originally sculpted by Kitty Cantrell. You can see more of her work at her website: http://www.kittycantrell.com/stonehorse.htm.
The Standing Draft mold was finished in 1996, and as you can see, on many of the models today, that original date is still marked underneath the back legs. The first painted release was a model called M.G.'s Prince in 1997, and you can view more pictures of him here: http://www.stonehorseref.com/Horseinfo.aspx?HorseID=4.