YUYAN SHUWU FOUR-CHARACTER HALLMARK IN BLACK ENAMEL, YONGZHENG-QIANLONG PERIOD (1723-1795)

Yuyan Shuwu, 'The Library of Washing Inkstone', is a hall mark used in the Yongzheng and Qianlong periods. An iron-red and underglaze-blue `dragon' wine cup and stand with this mark, also written in black enamel, was sold at Christie's New York, 20-21 March 2014, lot 2152. A set of four blue and white and copper-red wine cups with this mark, but written in underglaze-blue, was sold at Christie's New York, 15-16 September 2011, lot 1529.