I was at a gun show today and saw a decent looking original Winchester type 2 M1 carbine on the table for sale. While I was looking it over I noticed an allen head set screw screwed into the left side of the receiver about where the chamber would be. Rearward of the rear of the hand guard and may-bee a little forward of where an m2 selector switch would be. Also some of the stock wood that would of been up against the screw was whittled out of the way to make a clearance. It looked like it was done with a pocket knife or something. The dealer said it was his relatives gun that was brought back from WW2. Any of you guys have any idea what this was about? I have never seen anything like it. Thanks in advance.