Japanese ceramics were among the first in Asia to display impressed or incised marks relating to their makers. Such marks, emerging in the late sixteenth century on vessels made for use in the Japanese tea ceremony, indicate keen interest in the maker’s identity and skill. Marks began as “seals of approval” impressed by patrons who commissioned tea wares, such as the imprint of a large square seal—possibly owned by a Kyoto tea master—on a Bizen ware water jar. By the mid-seventeenth century, potters such as the Kyoto master Ninsei used elegant oval seals to identify their products. Ideally a famous person wrote the calligraphy for the seal. At the end of the seventeenth century, the Kyoto potter Ogata Kenzan introduced a new style by inscribing his own studio name in large brush strokes, sometimes even as part of the vessel’s decoration. Marks used at the Seto kilns, which were sponsored by a prominent warrior house, emphasized the prestigious ware rather than individual makers. Some Seto tea-leaf storage jars bore the name of a special local clay, “Sobokai,” incised on the base. Other tea jars bore stamped marks resembling the ciphers used as official signatures by warriors.