Raimey,
You are welcome to come anytime, but vise grips will never make such a mark, the serrations on vise grips are straight. It will take a bench vise to do it, and I have a couple set up and more laying around to try. I also have some take off Mauser barrels to try them on. Neither the Muenchen proof house nor the Melrichstadt sub. would put their mark in that particular location. BTY I have samples of the proper mark to compare with.
Mike