OK, I give up! I have used all my resources and still cannot find this maker's mark. It is on a large sterling silver serving tray which carries the Minerva mark with the figure 1 top right so I know it is French and 950/100 silver.
The first part is simple as it is Ste which, I believe, stands for Société but it is not the mark for Société Parisienne d'orfèvrerie which has an anchor and this one seems to have some type of plant.
Anybody got any ideas?