The piece you are talking about in Returning to Jedi has been the subject of much controversy in the prop world as the Harrisons claim it was made for filming a scene in which Luke builds his own saber in Obi-Wan's hut on Tatooine.It wasn't.It is a piece that was never delivered to Lucasfilm and has details which are not consistent with a piece that would have been made during or for filming.The crystal in the hilt is green and as many of you good folks in particular here will know the saber was originally meant to be blue and was only changed to green in post when it did not stand out clearly enough against the sky on the sail barge scenes.
It is a very nice saber but was not made or intended for use in the production and,despite what the Harrisons and ElstreeProps say,is a replica also.