It's not Japanese, it's a "chop" mark you can get made in (most any) Chinatown. They ask your name and assign it the closest homophonic Chinese characters. Then they carve your "name" into the stone chop, which is a stick, just smaller than a cigarette lighter. They don't usually inclue the American equivalent name in the chop. My ex husband and I each got one on a trip and I used it to sign my art for a while. Like this example:
