I don't have the books but I do have this bus. As you may have been guessing, I've been going through my childhood toys and have also been looking at my dad's collection.
According to Nick's online catalogue, only GPW buses had a smooth inner roof. Well, I thought I'd see if I can counter that with this poor example. It definitely has BPW although they are well used but also has a smooth roof.

Let me know your thoughts:



