The check digit is the 10th or 11th digit in a US VIN. It's derived from the other digits based on some formula presumably so you can't just make up a VIN.
So I guess the decision to make an M103 haul a W126 was made in Alabama.
I'm pretty sure the port of entry is NJ. My guess is that it lists Alabama along with Germany as a generic thing for US spec MBs these days.
I wish I had my SD VIN on me. It was a Euro delivery car. Imagine if it went to Alabama to be finished then back to Germany for delivery.