Hey ramit,
Break that rifle down and soak all of the metal in mineral spirits for an hour or so. Any old dried cosmolineor whatever should come off with a good wipe off.
The barrel should maybe precede the receiver by three months. That's not carved in stone, but ya' might be a little long in the difference. But......
If the bore is fine and the wood is good. Nothing to worry about.
Maybe the arsenal rework marks were sanded off by a prior owner, but for the price of the rifle and the good readings about ME and TE, it should be a fine shooter that you got for a fair price.
What are the markings on the bolt root top and bottom?
The big dogs will chew your bone and give you more info than me.
Bright flashlight is your best friend when observing a firearm in person. Like the Streamlight ones.
Lancebear