Yeah, this is one of those topics that generate a lot of debate. I know Lorenzo was able to study many examples of live, original guns, and made detailed observations regarding the history of markings and how things changed during the rebuilding programs. The differences of bottom plate markings, which kkkriverrats and I have been deeply immersed in of late, is one of the tales told conclusively only when one had the RSP still intact, so that a distinction could be made between guns that were still in original state and those that had been rebuilt. The RSP was always marked by the facility that rebuilt it, so Lorenzo found the patterns of component markings that were consistent with a rebuilt gun, and how this differed from the gun as originally manufactured.
My theory on the A6 specific parts is based on the fact that there are far more pictures of Korean period and later A6s than there are of WWII vintage. So one mostly sees guns with the later parts. But in my search of drawings and dates of origin of many parts, I am finding that many A6 associated parts did not appear until late in WWII or after. That cast top cover with the elongated hole is still something of an open question. The elongated hole is specifically an operation required by the one piece construction, as opposed to the earlier assembly where the extractor cam was a separate part, riveted in place. On the casting, the retaining slot for the cover extractor spring had to be milled from the top, hence the elongated hole. Now those covers were made by Saginaw originally, part of the ArmaSteel conversion efforts. What I have yet to find is the date that cover first appeared. I don't know if it predated the inception of the A6, coincided or came after. That is crucial to the question at hand. I am going to try and acquire that drawing and see if that can be determined. I'm just not convinced the cast cover was on WWII A6s from the inception. There seems to be little question that the 1950s production A6s had the cast covers installed. That still leaves open whether or not those were WWII SG covers from inventory or were new ones made in the 1950s. Both RIA and SAK produced the A6 in the 1950s. RIA made 5,421 and the SAK numbers have not come to light, same as for M37 production there. I have never even seen an example of SAK engraving for the A6, but I am scrounging up marked parts when I can find them. Man, I love the minutiae!
