Acorn mark with O/P inside stamp. There is one spot considered a missed glaze spot made during manufacturing process-EXCELLENT CONDITION! Cambridge Pottery was made in Cambridge, Ohio, from about 1895 until World War I.
The factory made brown glazed decorated artwares with a variety of marks, including an acorn, the name. Cambridge Pottery's artwares include ashtrays, mugs, pitchers, teapots, vases, and tiles.
Cambridge is one of the minor art pottery companies and because they worked only about twenty years, there is not much to be found.