Those would be cool. I’ve heard there’s piles of them in the high Sierra from the mountain warfare training center but don’t get around there much.
I found mine on top of Mount Takao just outside of Tokyo. We haven’t found any real valuable treasures yet but we’re having a great time digging. We dig pull about ¥7000 yen worth of modern coins out of the fields near the river though, so it’s always fun.