The neck made using cedro and/or mahogany is laminated with a strip of rosewood or Pau Ferro at its center, as found on the 1A model Ramirez III.
I thought few times to hide the central lamination inside the neck, but so far I still like that reference to this school of Madrid. I also believe the full rosewood strip helps to slow down the wear over surrounding cedro with the performer’s playing through the years; the cedro being softer than mahogany.