These stones were common in Japan before WW2, but are very rare today. The white stones are shell; the black ones are more likely not slate. They were made in the Miyazaki area of Japan. The black stones were probably from Osaka. They are irregular, some with flat edges, some slightly convex, others slightly concave. If you are a go collector, these are special!

If goban #141 is still available, they would go well together.