As far as I know,
The Whitneyville Dragoon has a Colt Walker grip and frame.
The first model Dragoon has oval bolt notches on the cylinder like the Walker.
The second model Dragoon has rectangular and beveled Bolt notches on the cylinder.
The third Model Dragoon has the same rectangular bolt notches and a rounded triggerguard. Some 3rd model Dragoons had leaf sights.
Hope this helps.