I took a photo of the inside of the shell body and I believe that you are correct C.W. I think it’s a MPC replacement as there’s no “R” or “Reproduction” stamping you see on modern replacement shells. I took a photo as well of it next to my 665's tender for comparison.
I don't see any signs of the web or post that would identify it as one of the MPC shells I described above.
There are an awful lot of reproduction tender shells that carry no "R", "Reproduction" or any other sort of markings. The only way to tell is to be very familiar with the "tells" in the castings. There are subtle ways to tell, such as the shape of the steps, the detail along the bottom edge, whether the lettering is hot stamped or silk screened. (And probably more)
I have a preference for the shells that were made by Bob Geller, I think they were the best quality outside of Lionel factory product. His older shells were marked "Foreign Tire Sales" or "RWG" inside. His later shells are unmarked.
One of the reproduction shells I purchased recently wasn't even painted, just cast in black plastic and lettered.
