A ruby-glass 'double-dragon' seal. Qing dynasty, Qianlong period. photo Sotheby's

of square form, surmounted by a pair of chilong clambering along the edge of the seal in pursuit of each other with their eyes locked, the seal face carved crisply in intaglio with the characters Wei shan yi wei bao ('being virtuous is venerated'), the glass of crimson tone mixed with black and deeper maroon coloured swirls - 6.9 by 6.9 cm., 2 3/4 by 2 3/4 in. Est. 400,000—600,000 HKD - Sold 500,000 HKD

NOTE: Imperial seals carefully designed and executed during the Qianlong era reached unprecedented heights in artistic craftsmanship with characteristics unmatched by earlier dynasties. Although seals were made in large quantities from a wide range of materials, ones made of red glass are extremely rare.

Wei shan yi wei bao ('being virtuous is venerated') was derived from Daxue ('The Great Learning'), one of the Four Books that describes many themes of Chinese philosophy and political thought. The phrase comes from a story from the Book of Chu - when an ambassador from the Chu kingdom was asked about the renowned jades from his home, he answered "The Kingdom of Chu never considers our beautiful and valuable jades as treasures. Instead, what we value the most, are our virtuous men."

Sotheby's. Fine Chinese Ceramics & Works of Art. 08 Oct 09. Hong Kong www.sothebys.com