Hi physoft, it is still an unanswered enigma as to the marks and their original purpose? There are several threads on this subject and even one most recent, to where I just corrected a miss-aligned barrel to receiver, and even with the marks aligned, or as nearly so as possible, it still didn't mean that all else was perfectly square and indexed properly???... I'd like to know more, but am at the end of my skill sets to discern any thing different then has already been discussed?... Best to you, til...lat'r....GT
