This is Sueki, early Japanese stoneware. The technique came from the Korean Peninsula in the 5th century, shaped on the wheel and burned hot in climbing kilns. The surface is blue-gray, the mark of reduction firing. Before that, Jōmon pots were made by coiling method and fired in open pits. This is what I like to do now too—shaping on the wheel, firing high. Not so different from then to now.