AmTiquing Trivia:

Clementson Brothers Pottery Mark

Clementson Bros.; Hanley, Staffordshire, England
In 1832 the present [1897] business was started by Reed & Clementson, Joseph Clementson shortly afterward becoming sole proprietor. In 1856 he purchased the Bell Works, formerly operated by William Ridgway. He retired in 1867 and died in 1871. His four sons continue the business.

1897 A Book of Pottery Marks by W Percival Jervis