ID of Studio Pottery Plate with impressed SP mark plus JC or JT mark

Hi,  Can anyone help identify the maker of this studio pottery plate?  I think it is stoneware clay, the backstamp has two raised circles with an SP in the first circle and a symbol in the second.  The plate is 10 inches wide and quite heavily potted.

Many thanks
Mary

Not a pair of marks I've come across before, and I'm not finding them in the Marks book. Possibly European or Australian/NZ
Helps to have a photo of the whole base to check clay and construction

Thanks Naomi,
Photo of the whole base attached.
Mary

The double foot-ring is not usual for British studio ware so I think a foreign origin is more likely

Thanks, I see the importance of plenty of photos now! Also I have just noticed that the back of the plate shows a terracotta tinge to the clay used. Hopefully someone will come along who recognises the pottery.
Mary