Thank you
My theory is:
While Roger Christian screw it up trying ot pass an original for a replica, changing his versión of events to accomodate that new finding of his, I still think he made the original ones. And I still think its true his versión of the events before his lie. I think its true he made just 3 of these lukes lightsabers.
I think this is one of those 3, that he gave to the special effects department to make the stunt saber. I think the sfx guys tried to put inside this saber the motor to make the rotating rod (explainign why is loose inside) It would not fit, or they were not capable of, they discarted this one, and thats why they made a stunt saber from scratch, using a metal pipe instead a graflex, and dressing it with some touches, as the red button, the knurled button (same kind like this one) and the grips. Black grips that my guts say are the ones this saber had at the begginning. They striped them off to put them in the stunt saber. Its known that grips were scarce.
The metal piece in the head could be a thing to try to put a static metal rod in it, like the did for the sequels. For use as rehersal or whatever.
That is my theory.