The marks in this thread consist of monograms--combinations of letters, including acronyms (like SECLA) or makers' initials (like CC)--used by unidentified ceramicists. If you can identify a mark, please notify the Moderator.
See also 6b and 7b. Mark no. 6 is not to be confused with the stamped or incised mark "PV" enclosed by a circle, which stands for the import line "Peasant Village." Perhaps no. 7 stands for California Ltd. Pottery Company?