I am no expert for sure, but I do know that the Dominique is a Rose Comb (sometimes referred to as a pea comb). Dominiques have NEVER had a single comb, that is what the Barred Plymouth Rocks have that is most different from the Dominique breed. Now, the site below also references a White Dominique (news to me).
http://www.dominiquechicken.com/Dominiques_and_Barred_Rocks.html
http://www.dominiquechicken.com/index.html
http://www.dominiquechicken.com/Dominiques_and_Barred_Rocks.html
http://www.dominiquechicken.com/index.html