The rifle is NOT a recovered drill rifle. The rifle simply has a battered cutoff from slamming the bolt rearward. And that's not uncommon.
You did very well and have a fine rifle!
J.B.
p.s.,
The rifle is a very desirable and valuable early production rifle and has the early style of receiver machining for the cutoff recess. The machining on Salt Flat's rifle is the later style.