>>63830918
I think it's meant for use in good visibility. When lighting is poor you use the "Christmas tree" aperture. All the later manuals I have however only describe the use of the "aperture" (the round peep) and the battle sight; nothing about the other three apertures on the sight. The peep was also customizable to the soldier: the standard aperture was .05" but anywhere from .04" to .10" could be fitted by an armorer. That >>63830647 is the "USMC No.10" sight set with just a .10" aperture and no other funny business. Here it is next to a standard .05" aperture.