Paul,
Dual means both good hunting and show results. In early days of 20-th century all English pointing dogs were dual dogs. Then these dogs been splitted into two separate groups: field trial and show dogs.
Today both trends are radical and especially in US, field trial dogs are very small and stand very far away from original standart and US show IRS are hypertrophy and just huge in size, they look like toys and most of them lost ability for hunting.
There are several good breeders in UK who breed dual English Pointers today, I saw these dogs here and they are just great, they win Intl shows and some of them are Field Trial Champs at the same time. One of this pointers is in my own city right now (pic1) and his son pic2 - all-Russian field trial champion 2006.
Dual Gordon Show and FT champ - pic3, Dual Engl. Setter - pic4.
What about dual IRS - we just began to work in this direction and collect all information about dual IRS allover the world. There is one very good dual IRS in Canada at the moment, who was 2-nd at some main Canadian amateur trials, unfortunatly I got no this owner address disposed, but I could search for it, if you want.