What you have are six lv 4 stones one iromono all stamped Narutaki. The stamps may or may not be correct and in the end don't really matter. The performance does. So it will depend on a few things. First how fine and grit rich each stone is and what type of edge you like. Plus your skills. I will say that seller usually under estimates his stone hardness level so it maybe some are more of a 4+ or 5 lv..
I really enjoy the edge from most iromono stones and they are usually easy to use.