Mirrors of this size and quality appear to be quite rare. It is a possibility that the current frame once held an embellished or enameled panel. See, for example, the large zitan pictorial screen dated mid-Qing period from the Palace Museum, Beijing and illustrated in Tian Jiaqing, Classic Chinese Furniture of the Qing Dynasty, Hong Kong 1995, pl.111. Another zitan frame, very comparable to the present lot, is also illustrated in Op. Cit., pl.112.