The only two patterns in the TCC database with J M & S have the initials in a printed mark cartouche with the pattern name "Vintage". Coysh & Henrywood attribute a Vintage pattern with J M & S initials to John Meir & Son with no image of the pattern. The impressed IMPROVED STONE CHINA mark definitely was used by Job Meigh & Son which means both potteries produced a pattern with that name. There were several other potteries that used the name "Vintage" for a pattern name. Sorry to be no help in your quest!