Original pottery vintage ad for the CLAYTON MAYERS COMPANY, LTD.  Main office and factory was located on North Circular Road, London, England. Crystolac Toughened Tumbler, virtually everlasting.  Each tumbler, manufactured since 1940, carries a code mark underneath the trade name on the base which indicates its year of manufacture. If there is one dot it was made in 1941, two dots in 1942.  1949 carry nice dots, but in 1950 the Roman numeral L appears. ​This old 1953 one-page ceramics trade magazine advertisement would display beautifully matted and framed.