That is correct. I have shown pictures that show the ESB helmet looking more narrow than the ROTJ and vice-versa. There are many factors that alter the appearance of the helmet's shape, i.e. the crooked mandible on the ROT, but all the helmets came from the same place.
Additionally, the dents on all the helmets are the same. Only the ROTJ helmet has a little extra damage dremmeled around one edge that creates a small gouge.But it is the same dent that is on the Empire and Prepro helmets.