*PLUMBERSSTOCK EXPERT* responded:
According to the manufacturer, this seat is "Natural Black Walnut" in color, "Natural Black Walnut construction", "Made with American-grown Black Walnut" and "Fully sealed with polyurethane".
Your description seems to match that of the manufacturer. I do not have one in stock or I would pull it out of the box to verify with my own eyes. I'm fairly certain this is the seat you seek. For more info, see this link (click here)