I'm sure the gas cylinder is GI but it's wide base. The front sight base is the same width as narrow base. No room for latteral movement. I had a Winchester come by here this morning and it was much like yours. Mostly Winchester parts, 2,200,000 number and the gas system was Springfield. Rear loop of the gas cylinder has a flat spot on top. Wide base. Narrow ear sight. Owens poppet valve gas cylinder lock screw. All the common stuff. It's not unusual for guns to be this way. Not surprising. If you order up Scott Duff's book on M1icon Garand, World War 2 it will show you all the pics to help you. Not expensive either, soft cover.