What part of M1 Rear Sights are Imperial/Metric

[Kano]

Which piece of the M1 Sight/M14 sight makes it imperial or metric?

Is it the elevation pinion? The aperture? or the notches on the reciever?

I know if you put Garand sights on an M14 they are imperial, but if you put M14 sights on a Garand, which part would make it metric?

 

[Claven2]

Its just the markings on the elevation drum that determine imperial/metric. Otherwise the parts are identical.

 

[Kano]

I feel a little silly, but that makes perfect sense. Thank you.