We had a question from a reader regarding the meaning of the various letter marks (B’s and C’s) not 
related to registration numbers or date marks found on the bottoms of some transitional period (1910-1915) examples of Newcomb Pottery. Examples of these bottom marks from two Newcomb vases are shown in the photos.
Accordingly the Walter Bob’s research, which is fully documented in Jessie Poesch’s Newcomb Pottery & Crafts, the B or B in a circle mark represents a buff clay body with a semi-matte glaze. This mark was typically used between 1910 and 1912. Between 1913 and 1915 the clay body and glaze mark was changed to a C or C within a circle. 
Between 1895 and 1907, there were several other letter designations used by Newcomb Pottery to identify clay bodies. Poesch’s Newcomb Pottery & Crafts book provides a full description of the years of use for each of these clay bodies and glaze marks on Newcomb Pottery.
