It is neither a prototype or a reworked gun. I own one of the handful that are out there and I am trying to get as much information on them as possible. I do know there was 30 made. STI had a some left over Dasan Machineries Bobtail frames and decided to make a Guardian Bobtail with them. I have seen a couple and the SNs I believe are in order. I do not know the first or last but the couple I have seen were a couple numbers away from mine.