The rear sight has the NM aperture. Rotation of 180 degrees changes elevation 1/2 minute. the rear sight base could be regular issue or National Match. The "clicks" of the NM sights are less than regular sights . If you lock the op rod back you should be able to see info on the barrel. You should be able to see a date and manufacturer. CMP sold several grades of Garand Rifles. The op-rod, trigger group, and bolt should be marked as to the manufacturer. Of course collectors are looking for rifles with matching parts.