Thank you Nick and Michael for the information and photos. It would appear to be on all Penn Central Dining Cars, and is probably a mold mark. It does not look like a physical break of the plastic shell.
I have had similar marks on HO 10-6 passenger cars. My dealer knows I detail all my cars with Preiser Figures and was probably aware that I would notice the marks and question it. The marks appear to be under the small windows. Hopefully the Dining Area Larger Windows are free of these marks.
Thank you again.
Sincerely, John Rowlen