Korean era SA gas cyl lock screw marking?

I'd like to find a period gas cylinder lock screw for my 4,268,xxx SA Garand. Any ideas what the correct marking would be? TIA

poppet style, O mark only. According to my little Scott Duff bluebook that is always in my case!

The Henry Owens screws marked with a large or small "o" or the P w/"o" are from 1952. My data also shows the Pw/ "crescent" is postwar. Of course all HRA and IHC screws would be post war.