Help needed: ID the maker of this wooden mortar & pestle bowl

[Nataku]

Seems like an odd question, but I honestly can't think of anywhere else to ask this. I picked up this very high quality mortar & pestle bowl today at an estate sale. The family was extremely wealthy, so I have no doubt it was expensive. I'm curious as to if anyone could ID the maker from the mark on the bottom of the bowl. It's Chinese or Japanese (they share some of the same characters), but beyond that I can't say much else. It's really nice and I'd love to find out the company that made it.

Any help appreciated.