This is what I was told by a retired gunsmith:
The (REP) stamp stands for "Remington English Proof" and is supposedly stamped on the barrel by the shooting gallery tech, after the rifle survives being fired with a proof load(special high pressure ammo that Remington uses to test guns with). I believe it then goes to have its stock fitted. All guns made by Remington, are supposed to be proof fired before they are shipped.
