RARE INSIDE-INSCRIBED ROCK CRYSTAL SNUFF BOTTLE SIGNED BAN SHAN AND YUN FENG, EARLY 19TH CENTURY of hexagonal section, raised on a short straight foot, the neck and lid with silver mount, the stopper of jadeite, inscribed in regular script on both main sides with an encomium, signed 'Ban Shan' and 'Yun Feng' and each followed by a seal of the artist, the interior of the four narrow sides inscribed with a four-line poem 6.7cm high (overall)