This is an antique bronze mirror from Tang Dynasty ( 618-906 CE). I acquired it from an antique shop in Vietnam during my work assignment there almost 10 years ago.
Diameter: 12cm (4 ¾ in).
Similar item with better condition was sold at USD3750 at Christie's in June 2011
References: (a) Masterpieces of Chinese Bronze Mirrors in the National Palace Museum Published by the National Palace Museum Taipei, Taiwan, (b) Later Chinese Bronzes by Rose Kerr, (c) Ancient Chinese bronzes by William Watson. (d) Circles of Reflection, The Carter Collection of Chinese Bronze Mirrors, (e) Bronze Mirrors From Ancient China Donald H .Graham Jr. Collection