David 66:
Here is a link that might help your investigation @ http://cs.trains.com/ctt/f/95/t/133652.aspx
link is from a Thread on Classic Toy Trains in 2010, and contains a photo of a Lionel(?) PH&D Boxcar,
The paint on the car (in my mind) sort of reminded me of Models of Cars from a number of years ago that were owned by the Port Huron& Detroit Railroad (PH&H) They were a dark blue with a white horizontal stripe. It also claimed the wording" The Blue Water Line" its main terminus was on the US Side at Port Huron, Michigan…
The line was I remember a privately held company ( Duffy?) it was sold to the C&O Railroad ( which was merged, or about to be merged into the CSX Corporate family. Not sure as to the specifics of that.
About 1970’s (?) AMTRAL (co-opted the Name Blue Water Express?) for a passenger run ( about 320miles from Port Huron to Chicago…I think that lasted til about middle of the 1980’s (?)
Hope this will give you some clues