Oh Garand of Many Sights
You gotta love Garand sights.
Hayden Foster over at American Rifleman has a great piece on M1 Garand sights, “From Flush Nut To T105: The Evolution Of The M1 Garand Rear Sight Assembly,” that is worth a read. Going past the typical fluff pieces often seen in gun publications, this one has some real scholarship to it.

The various versions of the M1 Garand rear sight knobs and pinions used throughout Springfield Armory production. They include, from left to right, the flush nut with short pinion, type one locking bar with short pinion, type two locking bar with long pinion, type three locking bar with long pinion, and a T105E1 assembly.
More here.