Usually, but not always the parts will either have a one or two letter MFG's code stamped on them.  In some cases, a number.
If you're getting a Carbine, get Scott Duff's "Owner's Guide To The M1 Carbine" at lots of places including www.fulton-armory.com.
Another spot to ask is the carbine forum at www.jouster.com
Oh, check the muzzle closely for signs of excessive wear to the bore caused by improper cleaning.  Can sometimes be fixed by re-crowning muzzle, otherwise it's a new barrel.
The carbine is designed to be sighted-in at 100 yds, with the rear sight at its lowest point.  If it shoots low, file the front sight, if high, then new, higher front sight must be installed and filed to suit.  Use GI ammo for sure in checking this.
The above assumed the adjustable rear sight, not the early two position "flip" rear sight.
Some carbines are worth much more than others.  condition aside, the manufacturer makes a big diff in price.
Let us know the Mfrs, and tell us the Ser #s, replacing the last 3 digits with Xs  (for example:123456 = 123XXX)
Good luck!