Alain,
Not to be to technical, but I note that the cars are very well braced with iron strapping and gussets. That said, on the upper and lower ends of the cars there is a flat plate that secures the roof, corner and side diagonal braces, or on the lower corner secures the corner, diagonal and floor braces.
My question is why do these plates extend beyond the end of the car? Am I missing some significance of them?