I have a general question Arsenal SAM7SF's that I haven't been able to find anywhere online.  On the left side of the receiver in the milled out portion where "arsenal las vegas" is engraved, there is a small notch towards the front/bottom portion of the window.  When I first received mine I thought this was some sort of manufacturing defect, but couldn't think what in the manufacturing process would cause this.  While searching through pictures online I started to notice that this marking was on all the SAM7SFs I saw to some extent, but there was no mention of this marking.  Any idea what this is???

IIRC this was discussed on another AK board at length and some of the more knowledgeable members stated it was caused by the receiver being locked into a jig for the hole being drilled for the rivet that holds the retaining latch mechanism for the folding stock when in the folded position.

Makes sense, my fixed version has no mark.