Will, thanks for posting the images of your set.
Lionel has two dome styles, P-S (Pullman Standard) with the "flat" windows and the Budd style with the contoured windows. Yours looks to be the Budd style, should it be the PS style? I'm not familiar with NP Prototype.
For the short vista domes Lionel has a Budd-like design, except the dome itself features flat windows like Pullman cars instead of the round Budd windows. The car seen here is an ACF design like UP used. I understand why they chose it. Northern Pacific Budd domes had slab sides instead of fluting and the dome itself looks better than the flat windows. It would be nice if Lionel would make a proper Budd dome like Atlas.