If you can, remove the rear handguard. You want to see the US ordnance wheel and barrel part number stamped there. I cant remember the number but tits different than the standard barrel part number.That at least will tell you the barrel is legit. You should expect to see post war upgrades to the rifle including the rear sights and a post war oprod.You should also expect a post war trigger group with all post war parts. Wide base gas cyl, cyl screw with valve. All other parts can be original to the serial range or post war. If you find wartime parts then its been messed with at some point in its life. Then you want to look for Arsenal markings to figure out what refurb it might have gone thru. If you find a narrow gas cyl on one then bubba touched it. If you find wartime trigger parts well thats tougher to say. Lumber is another story all together.
Lumber and markings can and have been faked. Metal parts can be faked but its harder to do and usually its just oprods.
Any serial range can be expected. Opinions differ on wether any maker can be expected, depends on the book you read.