Saginaw S'G' were built from any left overs from the S.G. plant as well as other makers. I have seen S'G' guns with S.G. components as well as IP parts and serial numbers. However, seldome will you see a factory installed S'G' part on a S.G. receiver. The General Manager of the GM gun plants, said that his job was to make Carbines and not worry about serial numbers or who would eventually wind up with what gun. (Source: Interview with Mr. William Doufner, GM of the General Motors gun plants, conducted by the Carbine Club circa 1980's) Rule of thumb for Saginaw made M1icon Carbines. What you see might well be correct. Never say never when Saginaw is concerned. If you are not already a member of the Carbine Club, I recommend that you join and buy the complete set of news letters. (The Carbine Club PO Box 235 Medway, MA.02053-0235)The newsletters go back to 1970. HTH.