Tobacco and Salt Museum, ed., Tokubetsu ten Namban bunka (Special exhibition of Namban culture) (Tokyo: Senbai kosai kai, 1981), no. 56.
For a nearly identical mirror signed Tenkaichi Sado see Kobe City Museum of Namban Art, ed. Kobe shiritsu namban bijutsukan zuroku Pictorial Record of Kobe City Museum of Namban Art, vol. 1 (Kobe: Kobe City Museum of Namban Art, 1968), no. 42.
The signature Tenkaichi was first used in the Momoyama period (1568-1600), after the title was bestowed upon outstanding artisans of metal-work, lacquer and ceramics by Oda Nobunaga (1534-1582). After the first quarter of the 17th century, artisans began signing personal names after the title, as on this example. By 1682, the Tokugawa government had stopped the use of the title completely.