Charles Collis, born in Birkenhead, England in 1879 (d.1966) began working as a young man at the Della Robbia pottery as a pattern designer. Very few pots were actually painted by him. His mark is usually the single letter ‘C’,.In 1900, at the age of 20 he left Della Robbia and went to work for Doulton & Co in Burslem, but returned to his former employer in 1902. In 1904 he departed Della Robbia for the second time, returning to Burslem and working for a number of different potteries. He returned to Della Robbia again in 1905, when the pottery was in its decline, leaving a year later to work for William Ault’s Pottery at Swadlincote where he remained for 5 years. His ceramic work ended with the outbreak of World War 1.
Collis’ memoirs are held by the Williamson Art Gallery, Birkenhead.
For excellent bio, see Hyland, Peter> The Della Robbia Pottery Birkenhead 1894-1906 (Woodbridge, Suffolk: The Antique Collectors Club, 2014): 150-9.