I am probably going to insult someone here, or there but stones like this one, a small plain gray koppa with all those stamps reminds me of an under powered small engine early 1970s yellow or orange Ford Mustang driving around town with a bunch of racing stripes and race day numbers on the side, and having to stop at the same stop signs the the station wagons have to. Way, way over done in the stamp catagory. I suspect that these stones are coming from the nephew of Kato-san, the last owner and the one who closed the Nakayama mine. His nephew owns the rights to the Oozuku mine and I might be wrong but I think it is him who has been stamping all of these stones for the past 5 years.
Alex