This ceramic is called Mino-yaki (美濃焼) or Mino ware that is a style of Japanese pottery, stoneware, and ceramics. It is produced in Mino Province, mainly in the cities of Tajimi, Toki, Mizunami, and Kani in Gifu Prefecture, central Japan. 

• Made In Japan
• Size: 4.75" x 3.25"
• Material: Clay
• Product #: 5090
• Code: NWS

No microwave, dishwasher, and oven.
Gently clean with soft sponge or cloth right after using.