Ray, My Rock Island serial number 64145 has a RIA 3-07 dated barrel and doubt it has been through any rebuild (bore is exc too) it has the early rear sight leaf and slide.

Have you and Fred noticed that some Rock Island rear sight leafs are without the top rib and have the square left side on the rear sight slide ? is this rear sight unique only to Rock Island rifles ? or could
it be found on early Springfield rifles too