CMPhas classified M1
rifles that are ready to be issued as "service grade". Lower grades are "field" & "rack". But, they always try to under-promise & over-deliver, so often folks think they were lucky enough to get one that is better than they paid for. I always inferred that "field" was well used, but still serviceable. "Rack grade" guns can be expected to have a barrel that needs replacement.
CMP hasn't graded their carbines, because they haven't really had enough to be worth the effort since the mid-'60s. I don't recall them using the term "grade" before sale of Bavarian carbines. For practical purposes, carbines are 100 yd rifles, & a tight muzzle is really not important; even with MW=3, they will still shoot "minute of pie plate". Plus, the pistol-class cartridge doesn't erode the throat like a .30-06 cartridge in the M1 rifle.
Neal