Leather Bag-Shaped Flask with Cover, 916-1125. Flasks like these derive their shapes from leather bags; even the edges are finely rouletted to resemble the seams of sewn leather. These were used by the nomadic Khitan people who established the Liao kingdom in Inner Mongolia, Manchuria, and North China. Such wares represented the Liao adoption of the Tang Chinese ceramic tradition, and yet they expressed ethnic identity and new innovations resulted from the cultural borrowing.