This flask is made around 581-630 AD, Sui-early Tang period. It has hard and thick slightly grayish red clay body. The dark intense green glaze flowed downward during firing due to low melting point/over heating that is coomon during that period. Due to 1500 years’ aging, the glaze has totally lost its surface shine and lack the “stickiness”feeling of newly fired ceramic’s glaze. Under careful examination the extensive crackle network. The crackle lines form numerous cells, about 0.2 to 0.3 cm on each side. With magnification, it can be seen that the intersections of the lines have lost to form minute holes. This is a genuine old ceramic. As similar one is in Victoria & Albert Museum, London.