Although of an unusually even yellow color, this range of material is thought to have been imported from the Baltic region via trade along the Silk Road. See the footnote to lot 207 for further comments on amber.
For a discussion on masks and circular rings as attributes of Palace workmanship during the mid-Qing period, see Moss, Graham and Tsang, The Art of the Chinese Snuff Bottle. The J & J Collection, no. 347.