Bev, from Kainga Happenings, asked me if I knew when my doves plate was made, so I did a bit of research.
This is the mark on the reverse of the plate.
According to this site, this mark was used at the beginning of the early 20th century by A. Lebacqz & M. Bouchart.
It's a bit confusing as there are many marks for St Amand porcelain (I think I would class it as earthenware, or simply 'china' although the French information definitely refers to it as 'porcelaine') and, although there is quite a bit of information on various sites, I have not been able to find out anything about Messieurs A. Lebacqz & M. Bouchart.
This led me to take another look at the plate I bought from a previous brocante, with a flowered pattern called Marie-Louise, in a similar shade of blue...
On the reverse side is this mark...
It seems that in 1818, Maximilien Joseph de Bettignies, a ceramicist from Tournai, opened a factory in the hamlet of Du Moulin des Loups at Saint Amand - the same hamlet on the mark on my Marie-Louise plate. According to the same site as I used above, this mark was used for long time - between 1896 and 1952 - a pretty good innings!
So now I think that St Amand china is a variety of china and not a manufacturer, referring to china that comes from the St Amand area.
Hopefully I will find out more about this later.