I agree with you. You are absolutely right. The car should be named 'Continental Mark II by Derham'. But every source I know, say 'Lincoln Continental Mark II by Derham'. That's the reason, why I accepted 'Lincoln' as marque's name...
I have two different sources: One of them states that car as a prototype, the other one, as made on private order... May be, someone has better informations...
The point goes to 'BattlePorQ'