Here are some interesting City Directory Advertisements that I found on Ancestry.com for Portland Stone Ware Co from Various Years. They are only a small number of the listing but the ones that had the full page graphics.
Portland Stone Ware Co Ad from 1918 Boston, MA City Directory
Portland Stone Ware Co Ad from 1924 Boston, MA City Directory
Portland Stone Ware Co Ad from 1875 Bristol, MA City Directory
Portland Stone Ware Co Ad from 1689 Portland, ME City Directory
Portland Stone Ware Co Ad from 1871 Portland, ME City Directory
Portland Stone Ware Co Ad from 1885 Portland, ME City Directory
Portland Stone Ware Co Ad from 1889 Portland, ME City Directory
Portland Stone Ware Co Ad from 1905 Portland, ME City Directory