gas cylinder lock screw

Sometime during the mid 1990's i was looking for some early Springfield 1903 parts from S&S Military parts in NY. I noticed they had some M1 rifle gas cylinder lock screws at $10 each, so I bought a few. When I got them, I noticed these were not common screws but very early variations and bought the remaining stock (6) from them. Also of interest, I noticed some of these lock screws do not have the bevel at the bottom of the thread. This was authorized in July 1941 but who knows how long it took to reach production ? Besides SA there are also Winchester screws in this group.Attachment 107830Attachment 107831Attachment 107832Attachment 107833

I take it the rough machine ones are Winchester? I have one here like that. The SA screw left with it's parent rifle a few years back...just a gas cylinder lock screw left now...one.