Great information. I checked the markings on my dad's M 722 in .222 Rem on the chart referred to above & found it was made in Sept. 1953. ( D ZZ )
The rifle was the first firearm he had bought new. it still shoots nice dime sized groups @ 100 yds.
Trigger control + Breath control + Sight alignment = Gun Control.
NRA Smallbore Prone Master