The sight aperture is not hooded. It is a standard rear sight aperture modified-by SA I would guess. Originally the rear face of the aperture was knurled, but the "plug" is not. The entire sight came off an early NM because the sight base is marked "NM" not "NM/2" or "NM/2A" of the later sights with the hooded aperture. The windage know is marked "NM" and does have the fine thread of the NM knob. I have tried to take a close up picture with no success. It came with a bunch of M1 parts that a team armorer gave me when his team switched to the M14icon.
FWIW