more angular. From the Sui dynasty period the calligraphy had become more rounded and thinner than before, and later during the Song and Yuan dynasties periods the jiudie (nine-folded) script was the preferred type of calligraphy. During the Qing dynasty period, most government office seals were bilingual with the Chinese (Seal script) inscription on the right side of the seal and the Manchu script inscription on its left. Personal There are many classes of personal seals. Private seals are naturally unregulated; therefore they show the largest variety in content, shape, size, material, and calligraphy of any type of seal. Seals with names, pen names, pseudonyms, etc on them were used as an early type of signature by people in their private lives. Artists would also sign their works and letters with their seals. Furthermore, Chinese literati are known to usually use a number of different pen names in their works, so trying to identify a person's name from a specific seal can be a tricky business. Name (名印) Denotes the person's name. Free (閑印) Can contain the person's personal philosophy or literary inclination. These can be any shape, ranging from ovals to dragon-shaped. Studio (齋印) Carry the name of the person's private studio (), which most literati in ancient China had, although probably in lesser forms. These are usually rectangular in shape. Art collectors' seals In Imperial China it was considered to be customary for collectors and connoisseurs of art to affix the print of their seals on the surface of a scroll of painting or calligraphy. Artists themselves often used their own seals on artworks, such as on works of Chinese calligraphy or Chinese paintings. Collector seals were chiefly used for the function of authenticating different pieces of art. Thus a collector seal identified to be of a famous art collector or connoisseur would become an integral part of an artwork itself and could substantially raise its monetary value on the Chinese art market. Thus in the course of several centuries, some Chinese paintings have become covered by a number of different seals of their different owners during the course of their existence. The Emperors of China also had their own imperial seals to appraise and appreciate art. As such, many famous paintings from the Forbidden City in Beijing tend to have the imperial seals for art appraisal and appreciation of generations of subsequent emperors on them. Leisure seals