Some Bokusho-mokkan (a narrow wooden strip on which some words are written in black ink called 'sumi') on which some Chinese characters are written, such as 'Kanotomi' (辛巳年),' 'Otsu-no-miko' (大津皇子 ［Prince Otsu]) and 'Okume' (大来), were discovered in the outer area of the gaikaku.
外郭の外側から「辛巳年」（かのとみ）「大津皇子」「大来」等と書かれた墨書木簡が発見されている。