The W5 was the Continental motor designation used by Durant.
My touring car is listed as a 1926, but has a lot of the earlier 1925 features. We in the Durant Motors Automobile Club, joke that Durant's moto was "no two cars alike". They even varied from plant to plant. This touring was made in Canada, I have another one that was made in California and is very similar but it has four wheel brakes and is a 1925.
You are correct about Rugby being used in the British markets because the Star name already existed there.
You can see a lot more info on our Club website