I hope that this is not an already resolved question, but I have not been able to find any information to make me believe I know what the mark is. On my Styer 1940 Mauser 98k, I have found a mark. I have read that this may be a Russian capture mark. I have heard these capture marks described in different ways, but have never seen images. This mark is on the left side of the receiver, and an almost identical, but smaller mark is on the barrel stem. I bought this rifle from a dealer/importer who is a somewhat person-non-grata to many, and it was even been posed that even a fake mark has been perpetrated by this person. I will post some pictures (hopefully) and if anyone knows for sure what this is, please reply. I will say that I do think this was a Russian capture as the serial number is stamped into the stock on the left side below the bolt take down disc, and the bolt has evidence of being brushed off where the electro penciling of the serial number might have been. I am very happy with this rifle where ever it came from.