Ceramic cigar ashtray (!) marked with an intertwined ST (or TS) within a stylised vase or jar

Hi, I am clearing our my parents house and I came across this rather wonderful ceramic cigar ashtray. It has a few chips on the underside, but it is a lovely piece of pottery and extremely decorative. It has a very distinctive mark, but I can't find a reference to it anywhere. Anyone got any ideas on the maker please?