E.P. Charlton & Co. was a a variety store chain with stores in Massachusetts from 1890 and in California from 1904. The 1904 Crocker-Langley lists "Charlton E P & Co (E P Charlton) varieties 943 Market". After the 1906 earthquake/fire, the 1907 Crocker-Langley lists "Charlton E P & Co. bazaar, 1315 Fillmore and 2554 Mission". Charlton postcards indicate "Published by E.P. Charlton San Francisco" (or Oakland or Los Angeles), but the cards were produced for the store by other publishers (notably Mitchell). Some Charlton cards have stock numbers, but many do not. Charlton was consolidated into F.W. Woolworth in 1912, so later postcards indicate "Published by F.W. Woolworth San Francisco".
Steve's SF postcard pages: