An identical Dingyao vase with an incised guan character on the base from the Nelson Gallery-Atkins Museum, Kansas City, Missouri, is illustrated in Sekai Toji Zenshu, Shogakukan Series, vol. 12, col. pl.1, and in Toki Zenshu, vol.14, Liao Ceramics, pl. 46; another from the Charles B. Hoyt Collection in the Museum of Fine Arts, Boston, is illuatreted in the Catalogue, no. 2, where the authors discuss the mark guan (official) suggesting that these wares made for official use were found only in excavated tombs dating from between A.D. 937 and 958. They refer to a third from the Liaoning Museum, Liaoning Province. A further example, excavated from a royal Liao Tomb in 1956, is illustrated in A Selection of Liao Ceramics, Wenwu Publication, no. 46; the group of white wares inscribed guan and xinguan is discussed in Wenwu 1984-12 by Li Huibing where he notes that to date, only Dingyao pieces bear the guan inscription and that both those and the xinguan-inscribed Dingyao examples occur in the late Tang Dynasty and early Five Dynasties period and discusses the characteristics of these wares concluding that these were all produced at the Ding kilns at Quyang